The title has been leaked, allegedly, although currently it's just floating around the internet with no proof that it hasn't just been suggested by a nobody.

The title is alleged to be (highlight to see it) The Final Problem.

I'm not convinced yet. For one thing, it would be the first time they've used a title of an original Doyle story with no tweak to it. Secondly I can't see why they felt it necessary to hold the title back when they released the other two titles, because it's not that much of a spoiler or a hint to what might happen in the episode. The only 'hint' with this title might be the return of Moriarty, but let's face it, we're all expecting that in some way or another anyway.

The episode title has now been confirmed.

Why do Sherlock and company resort to subterfuge to break into Sherrinford? Mycroft at least can come and go as he pleases, so why all the guff about him being in a coma? OK, there's a chance that the security might be compromised but when it turns out that the security is compromised, both Watson and Mycroft seem surprised.

Eurus says that she wouldn't do anything as clumsy and obvious as blow up Molly, but didn't she just do that to 221B Baker Street? In fact of all her moves this series seem to have been fairly clumsy and obvious. And how could she be sure that the trio - without whom her Death Maze couldn't work - would all survive the blast?

In fact why has Eurus waited so long to make her move? Her entire motivation is about getting Sherlock to pay attention to her, and she's clearly able to come and go as she pleases. Even if she's done some sort of deal with Moriarty to let him have first crack at Sherlock (and why risk the prospect that he might succeed?), Moriarty's been dead for a while now. Her actions in earlier episodes are focused on Watson, which implies that she's needed him as the new "Redbeard" (though as with her deal with Moriarty the details are a bit vague), so it clearly had to be at a time when John a) knew Sherlock was alive and b) wasn't blaming him for Mary's death - but there have been lots of opportunities for that in the interim, but she deliberately stalls after the first "miss me?" tease. Was she waiting for the renovation work to turn Sherrinford into a Death Maze to be finished? Couldn't she have improvised instead?

The transcript is now complete and can be found here.

On the BBC, this episode received the lowest viewing figures of any episode of the show ever, whereas Thatchers three weeks earlier had over 10 million viewers, more than any other show over the Christmas period, including the Queen’s Christmas Day message. I have my theories as to why so many people abandoned the show after Detective which was, in itself, one of the most spectacular and beautifully filmed episodes ever.

(1) John’s violence towards Sherlock. The average viewer hasn’t spent years analysing John’s character and, to most people, seeing John – who’s very much the everyman of the series with whom people can relate – beating the living daylights out of a junkie who’s too weak to defend himself was simply intolerable.
(2) Culverton Smith was simply too similar to a real-life British monster. The real-life man was exactly like Smith: a massively popular celebrity who, while very eccentric, was loved by the public, and who raised millions for charitable causes and particularly for a hospital. He was knighted by the Queen for his services to charity, and any uneasy rumours about him were quashed by the establishment and the BBC in particular. It was only after his death that people started coming forward to talk about the terrible abuse he had inflicted on them. There are also dreadful rumours (not substantiated, I think) about what he got up to with corpses in the morgue. These revelations only started coming out in 2012, and the knowledge of what he got away with is still raw with the British public. Putting a carbon copy of him on a TV show which is meant to be entertaining was in incredibly poor taste. I can’t imagine what Steven Moffat was thinking, and I’m surprised that Mark Gatiss or either of the other producers didn’t stop him.

The actress playing the young girl on the aeroplane was also in Scandal. She was the one of the two girls wedged into the client chair together who told Sherlock, “They wouldn’t let us see Granddad when he was dead.”

When the home movie footage keeps cutting into the film that Mycroft is watching, after the words “I’m back” first appear, it seems as if the black & white film returns for a second, showing a close-up of the actress’ eyes. Pausing that moment, I realised that it’s actually Eurus’ eyes. This whole scenario was set up by Sherlock, so how did he get a photo of her? I wonder whether Mycroft actually fantasised that moment after seeing the message.

But if Sherlock got hold of home movies, why was Eurus in none of them? In the footage, Sherlock looks to be about four. Was three year old Eurus the one who was holding the camera?! (Fandom theory is that it was Uncle Rudi doing the filming!) Or was all family film edited to remove every trace of Eurus after they realised that Sherlock had completely forgotten her?

In typical horror film style, to make the scene more dramatic the film spools off the end of one of the reels and flicks around noisily. Unless Mycroft has a valet who normally loads films for him, he should have noticed that the original movie – which didn’t seem to be getting towards the end, going by the dialogue – was too short when he loaded it.

I laughed with delight when Mycroft pulled a sword from his umbrella. Mark Gatiss has been saying in commentaries for ages that he thought there should be a sword in there, so I was chuffed that he finally got his wish!

The first portrait which starts to bleed as Mycroft passes it is actually based on a photograph taken in 1976 of Timothy Carlton, who plays Daddy Holmes. In that photo he was posing with his wife Wanda Ventham, who plays Mummy Holmes, and their newborn son Benedict Cumberbatch (‘Carlton’ being Tim’s acting name).

Did Sherlock really ruin all the family portraits with the blood running down them?! Or had he covered them with something first to protect them?

When Sherlock said that Eurus had only shot John with a tranquilliser I was originally calling ‘foul,’ but went back to rewatch the last seconds of the previous episode and there wasn’t a loud gunshot as I had originally assumed.

It’s a shame that they cast a girl with brown eyes to play young Eurus. Was there really not a blue-eyed actress of the same age available?

We see an overhead shot of the drawings that young Eurus has done, most of them depicting bad things happening to Sherlock. We then cut in to a close-up and suddenly there’s a new drawing of a tombstone marked “RIP Sherlock” which wasn’t visible in the overhead shot despite being it very close to the picture she’s working on.

All things considered, it’s a miracle that Daddy Holmes sounded so cheerful when he told Mary in His Last Vow that his wife gave up work for children. Seeing as they raised a robot, a drug-taking high-functioning sociopath and a psychotic murderer and arsonist, it’s amazing that the Holmes parents are still sane and have seemed so cheery before now!

When the drone smashes through the kitchen window, we can see down the hallway to Sherlock’s bedroom and the door is closed. Either he has started doing so after all these years, or someone on the production crew forgot to leave it open! (Probably because it would have been too expensive to build the set behind it, but they could have at least left it ajar and in enough darkness that the set wasn’t needed.)

Considering that any motion will set off the ‘patience grenade,’ both John and Mycroft move quite a lot! Sherlock, on the other hand, sensibly barely even moves his lips whenever he speaks.

Someone online beautifully pointed out one of the many examples of the development of Sherlock over the years: from A Study in Pink when he asked – in relation to the dead woman in pink – “Why would she write her daughter’s name?” to this episode when he wonders if John can say goodbye to his daughter before the grenade explodes.

And yes, of course John wouldn’t be able to have a conversation with Rosie but at least he might be able to hear her gurgle once last time.

The scanners at Sherrinford are pretty poor if they don’t detect the earpiece which Sherlock is wearing. Surely it must emit a detectable signal?

Sherlock tells Eurus in her cell that she came to his flat “a few weeks back.” That suggests that little time has passed since the explosion in the flat and yet Sherlock, John and Mycroft show no sign of any injury. At the very least they ought to have burns on their backs and hair and Sherlock and John should have multiple cuts and bruises from crashing through glass onto the street at speed from a first-floor window. (In a behind-the-scenes documentary released online the day after the episode, Gatiss said they were about to film the boys “falling onto the awning of Speedy’s” but the actual footage shows them being propelled far further out into the road.)

Why does Sherlock so stupidly ignore a “Vatican Cameos” warning from John? Regardless of his emotional state at the time, he knows that that’s something you should never disregard.

Eurus gives Sherlock her violin and he asks how she knows that he plays. Idiot boy, she was in your flat! You just said so, and there’s always music and a music stand scattered around the place, and your violin case is usually lying around in plain sight!

Where exactly is Eurus wearing her throat mic? Her entire throat and neck are visible. Is it embedded inside her neck?! And despite that, shouldn’t Sherlock have realised that he could hear the violin unmuted, and then hear her ‘real’ voice when he gets close to her? The speakers aren’t loud enough to obscure the ‘real’ sound of either the instrument or her voice.

The entrance to Eurus’ cell is a lift to an upper floor. How do the guards arrive so quickly after she screams out to them? Were they lurking in there for ages awaiting her call, frantically holding the door closed all the time?

When “Five years ago” came up on the screen after Moriarty’s arrival, many fans were hurling popcorn at the screen and yelling, “Boo!” at being misled that he was still alive, which would have given us the biggest surprise of the series so far (or the final arrival of the twin-which-it-never-is). I didn’t do that. But that’s only because I didn’t have any popcorn and I didn’t want to risk lobbing the remote control.

Mycroft is not at all his usual powerful self when he refers to Jim’s interest in “my little brother.” He’s also surprisingly over-emotional when the governor and his wife die. This is the man who sat with his feet up and calmly watched his brother being beaten in Serbia and then was snarky to him after the torturer left the room. My only explanation (apart from shoddy writing by Mofftiss) is that his shock at having been so played by his sister did something to his emotional state.

If Eurus planned all this five years ago and roped in Jim to harass Sherlock, why did she allow the man she knew had a death wish to almost bring about Sherlock’s suicide from the roof of Bart’s, yet arranged for the “Did you miss me?” message to save Sherlock from dying on his Eastern Europe mission?

Probably only British readers will get this, but I cracked up when I saw a comment on Twitter – in relation to the various tasks in different rooms – that they hadn’t realised they were watching an episode of The Crystal Maze!

Throughout the ‘tasks’ the boys keep talking about how and whether they can save the little girl. Nobody ever mentions the many other passengers on the plane! Do they assume that they’re all dead rather than just unconscious? Maybe the Holmes brothers think that this is another ‘Flight of the Dead’ but Doctor Watson should be thinking more about everyone on board.

The phonecall between Sherlock and Molly was heart-wrenching, especially when I was writing every little moment second by second. By the time I’d finished it, I wanted to smash up the place.

I had my hand over my mouth when Sherlock pointed the gun at Mycroft, whimpering, “No, oh no, oh no,” and genuinely fearing that Sherlock might have to do it.

After Sherlock is darted to prevent his attempt to shoot himself, there are a few very rapid flashbacks to his past. One of them is a very fuzzy out of focus shot of something round and dark blue and I’m sure it’s meant to be an overhead shot of the well. Why would this be in Sherlock’s memories when he never found it or even knew of its existence? None of the family (apart from Eurus) could have known about it because it would have been one of the first places searched when Victor went missing.

In the overhead shot of Sherlock lying face-down on the table, there’s no sign of all the photos which he then finds on the walls.

I have to reblog this comment from someone called grandpa-vinegar on Tumblr because, much as I am trying to love this episode, this cracked me up:

I cannot stop laughing just imagining some cartoon cronies hammering that 10 x 10 room together in the front yard and stapling pictures to the walls for dramatic effect while Sherlock just lies like a dead-ass tuna in the middle of it. You know those minions were watching from the bushes with binoculars like, “D*mn good touch with the dog bowl, Stanley.” ... Did Euros shout commands at a team of stage hands with a megaphone to set that all up before she had her level ten psychotic break? How did they transport two grown-ass male bodies to the yard in that amount of time? Is Euros a licensed pilot as well as a criminal mastermind and movie director? Where were all of the cronies that helped her set it all up? Were they all posted up in Mr. and Mrs. Holmes’ bedroom watching “The Great British Bake Off” while Sherlock ran screaming through the yard?

The revelation of the ‘real’ Redbeard was heartbreakingly tragic. But I love the name they gave to the boy. In the Doyle canon, Victor Trevor was indeed the only person who Holmes considered to be a friend before he met Watson. He knew Victor at university. In a clever link with the dog motif, they met when Victor’s dog bit Holmes in a park.

When Sherlock finally realises what happened to Victor, there’s a cut-away to the swimming pool where Sherlock and Jim had their stand-off in The Great Game and then to Victorian Holmes at the Reichenbach Falls. Eurus says that Sherlock has had “deep water” in all his dreams all his life. This makes no bloody sense at all and is terrible writing. Even if he has dreamed a lot about deep water, possibly prompted by little Eurus’ repeated descriptions of Victor as “drowned Redbeard,” he’s not afraid of water or he would never have suggested the pool as the meeting place for him and Moriarty, and he would have had a panic attack while fighting with Ajay in Sandeford’s pool. So why did the writers make it such a big thing here? And they’ve even built up to it during this season, especially in Thatchers when he kept being overlaid by dark rippling water whenever he started to get any kind of revelation. If it really was supposed to be significant, it should have happened in previous seasons as well.

How did Sherlock know in which order to put the numbers from the gravestones? He puts those from Nemo Holmes’ gravestone last. If Eurus’ repeated reference to “no-one” was a hint for him, wouldn’t they go first? And how did Sherlock know exactly where to stand, because it doesn’t seem that he takes the numbers from all the gravestones. Also, there are umpteen repeats of the number ‘1’ so how does he know which of the ‘1’ numbered words should go where? That whole cipher-breaking scene made no sense, made worse by the fact that – in order to get the words in the right order – he treats the second large verse as the fourth.

So the murdering psychopath just needed a cuddle to make everything all right?! Okay ...

Many people online have ranted about the uselessness of someone throwing a rope down to John in the well when his feet were chained. I don’t understand the fuss. I saw it as someone about to climb down the rope with a bloody great set of boltcutters, and also John could use the rope to help pull himself a little off the ground – to the full extent of his chains – and keep his head above the water until they arrived.

Greg says that he’s spoken to Mycroft, who was locked in Eurus’ cell. Even if it took a few hours for the police to arrive at Musgrave Hall, it should have taken a whole lot longer for reliable people to fly out to Sherrinford and take over the place. They couldn’t have just made a phonecall because so many of the staff were under Eurus’ influence and so nobody could be trusted.

I burst into tears when Greg did his “great man/good man” bit, especially as that was always my Best Line from the first season.

In the burnt-out living room of Baker Street, Sherlock finds the skull from the wall between the windows lying near where his chair was and John finds its headphones at the other side of the fireplace. How did they get blown further into the room when the blast should have thrown everything outwards? Both items should have still been near the wall.

During the final montage, John sits and looks at a chalkboard in front of the fire with lots of stick figures in different poses drawn on it. Referencing the Doyle story, “The Adventure of the Dancing Men,” someone on Tumblr found the letters of the alphabet to which each figure applies and said that they read:

NEVAGONA
GIVEYOU

It would be glorious if it were true and Mofftiss had ‘RickRolled’ the entire audience but sadly it turned out that the Tumblr image had been Photoshopped. (See my later post for the true translation.)

So it never was twins! When I first saw the boy who we then learn was Sherlock’s best friend Victor, I overlooked his red hair and assumed he was Sherlock’s twin brother. I also initially assumed that the arrival of Moriarty at Sherrinford was Jim’s twin.

And we still don’t know what Lady Smallwood’s first name really is! I’m now more certain than ever that an early draft of the script of His Last Vow called her Alicia and her name was changed to Elizabeth later, but someone in the production team forgot or was working from the early script when they put her name onscreen as Alicia in Vow and someone only noticed after a mastertape had been sent off to the DVD makers, and corrected it for the BBC version. Then they forgot again when making her card for Detective.

I’ve probably got a lot more to say about this episode, and about the season overall, but I haven’t slept properly for weeks and the DVD will be turning up in a day or two and if it’s got Extras on it I’ll have even more work to do, so this’ll do for now.

Season 4 finale.
Intriguing that this begins with a girl on a plane with everyone else unconscious.
Fascinating how all this ties in with Eurus.
Eurus certainly proved terrifying and what a horrifying revelation about Redbeard the dog.

As of this moment, Steven Moffat and Mark Gatiss are yet to determine whether they want to make a fifth season although Benedict Cumberbatch has already signed on for such a season.

If the season 4 finale does turn out to be the series finale than its title is a very fitting one to have as the ending certainly feels like the ending to the series.

Wow, after all the good will built up by the twist ending of last episode TPTB then go and •••• it all away with a stupid psychobabble episode.

I am sick to death of writers trying to write crazy people, because most of them can't do it well, and the writers of this series are no exception.

Oddly enough PBS aired A Study In Pink after this ep and I find a certain thing interesting.
Here Watson refuses to shoot the governor because of his morality, but he had no such qualms when it came to shooting the guy in the room with Sherlock and couldn't hear anything they were saying and may have had no evidence the guy was actually the murderer.
I'm not saying Watson should have shot the governor it's the supposed morality being given as a reason, but where was that morality when John shot an old guy that Sherlock was talking to?

Surely it's just consistent with Watson's usual characterisation as Not a Murderous Psychopath Who'd Happily Murder an Innocent Man Just Because a Genuine Murderous Psychopath Orders Him To?

Part of the problem here is as I was writing about the interesting comparison I found myself thinking more and more about the Pink scene and trying to tie it into my comments on this episode instead of just going to the Pink board and listing the possible nit of that episode there.

There were a few good reasons for Watson to not shoot the governor, I just thought morality was weak when a better argument would be "if the governor's wife is killed it's because you, Eurus, choose to kill her." Put the blame onto the actual person at fault rather than try and force it onto Watson.

Murder an Innocent Man
Is the governor innocent? Wasn't he working with Eurus?

Yes, he was, but he was apparently programmed to work for her, rather than with her. And whether he was so weak that he succumbed very easily, or she promised him power/wealth and he was greedy, I'm not sure he deserved death.

Then again, the fact that he never once referred to his wife by her name pissed me off more than anything else!

It does seem, however, a little early in the "tasks" for any of the captives other than the governor to be taking Eurus' threats so seriously that any of them is prepared to execute the man. OK, they know that she's bonkers in the head and has already killed the therapist just to get access to John (and why, if she wasn't going to do anything drastic with him? Why didn't she reprogram him to work for her?). I can only speculate that Sherlock - having just been near-suffocated by her - realises how dangerous she is, plus there's the girl on the plane that they're trying to save * and so he does take her threats seriously and John, as always, takes his cues from Sherlock.

* Let's not go there. Did any of them, even John, really ever believe that they could guide a terrified 12 year old to even find the autopilot, let alone work out how to turn it off and then fight the steering column, control the flaps, drop the undercarriage and get the plane down safely?! Even once Mycroft made it clear that the only sensible thing to do was to get her to crash the plane into the sea, she would still need to disconnect the autopilot so that the plane could fall out of the sky.

Let's not go there. Did any of them, even John, really ever believe that they could guide a terrified 12 year old to even find the autopilot, let alone work out how to turn it off and then fight the steering column, control the flaps, drop the undercarriage and get the plane down safely?! Even once Mycroft made it clear that the only sensible thing to do was to get her to crash the plane into the sea, she would still need to disconnect the autopilot so that the plane could fall out of the sky.

How modern of a plane was it, because the autopilots on modern planes can land on their own, they only have to be commanded to do so.

That may be why Sherlock was asking her to look for a radio, but if he couldn't even describe what it might look like, he apparently hasn't memorised the layout of your average cockpit.

After Mycroft has been chased downstairs by the clown and then Sherlock arrives and the lights come back on, when the man in the dress comes out of a downstairs hallway there’s a table beside him with a photo of a young Tim Carlton and Wanda Ventham (aka the Holmes parents) on it. Also, to the left of the clown up on the landing, in between the uprights of the balcony there’s another historical portrait on the wall, and this one closely resembles Benedict. I wonder if Ben and Mark Gatiss were allowed to keep the portraits that looked like them?

When Mycroft is at 221B and telling Sherlock about Eurus, he has a flashback to their childhood. Why is Redbeard the dog in Mycroft’s memories? It ought to have been Victor.

When the drone lands, Mycroft expresses concern about the café below the living room and Sherlock has to reassure him that it’s closed. It seems that Mycroft’s knowledge of the strength of the explosion (or the strength of 221 Baker Street’s ceilings/floors) was faulty, because the floor is perfectly fine afterwards.

When the grenade explodes, the fireball sweeps across the floor enveloping – amongst other things – some sheet music. One of these is clearly Sherlock’s wedding waltz, including his message to John and Mary written in the corner. Some online fans heartbrokenly decided that John’s ‘anyone but you’ message which Molly handed to Sherlock outside the Watson residence at the end of Thatchers was an envelope simply containing the sheet music and nothing else. Unfortunately, other fans – including me – suspect that someone in the production team found the music in the props cupboard and just added it to the debris without even thinking about whether it made sense for that piece to be in Sherlock’s flat instead of in the Watsons’ wedding album.

Neither John nor Sherlock has his arms across his face when he goes through the window, yet apparently they both make it through the glass – and the frames – without getting their faces ripped to bits. Presumably they were mostly propelled by the blast rather than their own impetus, and I tried to excuse the ease at which they went through the windows by wondering whether they were only single-glazed, which would have helped a bit. However, those windows were blown in during The Great Game in 2010. Nobody in 2010 replaced windows with single glazing.

In my earlier comments I said I was surprised at how little sign of injury John and the Holmes boys were showing at Sherrinford in light of Sherlock’s comment to Eurus that she (as Faith) came to his flat “a few weeks back.” I’m now thinking that either Sherlock or – far more likely – the writers have no concept of the passage of time. It must be way longer than ‘a few weeks’ after her visit because since then Sherlock had to build up a profile of Culverton Smith (while off his head on drugs) and be sure that this was the man from whom John would need to rescue him, then he had to wean off the drugs afterwards and recover from the malnutrition and wait for his kidneys to get back in full working order etc, and by the time you add in recovery time after the explosion, it’s likely to have been months ago. This “Oh, it was some time ago; we can’t be bothered to work out how long” attitude is reinforced later in the episode when Sherlock says, “A moment ago a brave man asked to be remembered,” when in fact the governor shot himself ages ago even in episode time, and we missed the time between Sherlock smashing up the coffin and being slumped on the floor.

If Sherrinford is such a top secret place, who is broadcasting its name to nearby shipping, and why is that name coming over official radio channels?

Despite watching the episode umpteen times already, I still can’t work out what accent Sherlock is using when he masquerades as the guard. I was totally convinced it’s a Northern Irish accent – in fact I was about to say in the transcript that it’s a Belfast accent but decided to leave it more generic – but many people have said they think it’s Scottish. I can concur that some words could be either but the overall accent still sounds Irish to me, and I also think it’s more likely that the writers wouldn’t make both Sherlock and Eurus use Scottish accents because it would be too coincidental. Until/unless Benedict gets asked the question in a future interview, I may never know whether he’s rubbish at accents or I have terrible hearing!

Presumably Eurus must have sneakily been repeatedly nipping in and out of Sherrinford for years. She has been locked up in secure institutions since she was about six, and specifically incarcerated at Sherrinford “since early childhood” according to Mycroft, and even if she was given more outdoor access and more integration with other people before she destroyed her first institution and was moved to Sherrinford, since then she has been “allowed the strict minimum of human interaction” – again according to Mycroft. Surely going out into the world for the first time in years, probably decades, would have been complete overload for her and she wouldn’t have been so comfortable playing the woman on the bus, and Faith, and the therapist.

If Sherlock turned his memories of Victor into memories of a pet dog, why did he say to his Mind Palace Redbeard in Last Vow, “They’re putting me down too, now”? Additionally, in his drugged-up Mind Palace in The Abominable Bride, when Watson asks him, “What made you like this?” he says, “I made me,” and then seems to hear a dog whimpering in pain. If Victor’s disappearance was so traumatising for him, wouldn’t he have given himself nicer memories of the dog’s departure from his life? I would have thought he would have imagined that the dog ran away, or ‘went to live happily on a farm’ or even died peacefully in Sherlock’s arms of old age.

Who sent the DVDs from Mary? Did she have a trusted friend to whom she could say, “If I die, send this one to Sherlock after x days, and this one to John x days after that”? Or did she make arrangements with a solicitor or someone similar to send out the correspondence if she hadn’t contacted them for a specified amount of time and/or they received news of her death?

Someone told me the proper translation of the ‘dancing men’ chalk figures, but it’s taken me this long to check that the person was correct. The figures read:

AMHEREAB
ESLANEY

as in “Am here Abe Slaney”. Abe Slaney was the ‘villain’ in Doyle’s “The Adventure of the Dancing Men.”

The unconscious Viking lying on the floor of 221B during the final montage was played by musician Paul Weller. I believe that he and Martin Freeman are friends, so presumably Paul is a fan of the show and maybe asked Martin if he could wangle him a cameo role.

An unresolved general issue: why does Mycroft now only call John “Doctor Watson”? The last time he used his first name was in Reichenbach and in that and in the earlier Scandal and The Great Game he comfortably called him ‘John.’ They didn’t speak onscreen in Season 3, and in the Special we only saw Mycroft address him once (during the scenes that took place in the present) and that was on the plane when he asked him to look after Sherlock, so it sort of made sense to call him “Doctor Watson” there. But why is he now using his formal title all the time? Is it because of how he apparently put Sherlock in harm’s way by giving Jim so much information about him, and now Mycroft feels that he can’t be on friendly terms with John? Or is he actually being more polite this way and showing him greater respect than treating him like Sherlock’s little friend?

This is hilarious: it's a short gif theorising how - according to Mark Gatiss - Sherlock and John fell safely onto the awning of Speedy's cafe after the explosion. The "Boop! And they're fine" line was said by Mark in one of the DVD Extras when they were filming Benedict and Martin doing the jump.

There’s an odd cut during the flashback scene where little Eurus is in her bedroom at Musgrave Hall drawing horrible pictures of Sherlock. She looks up and we clearly see her brown eyes. Then she picks up the box of matches and shakes it, and then there’s a close-up of a lit match reflected in her eyes – but now they’re blue. From the shape of her face I’m fairly sure that that shot is of Honor Kneafsey, who played the girl on the plane. I don’t know whether they couldn’t trust Indica Watson (playing the younger Eurus) anywhere near matches, or whether it’s supposed to be some significant clue. It doesn’t really make any sense when the Honor version of Eurus never really existed. Or maybe it was a practical problem: they didn’t have time to do that shot with Indica and so filmed it while Honor was on set. Or maybe Indica got scared of having a flame so close to her face and wouldn’t film the scene.

It still doesn’t explain why Eurus’ eyes changed colour between her being six years old and ten years old.

Many babies are born with blue eyes that darken to brown as they age. Eye color going from brown to a lighter one, like green or grey, also happens, although not as often and usually not as quick. Dramatic changes as described here can also be a symptom of serious eye disease. The real explanation is probably like you said though, they shot the scenes with the available actresses and didn't care about those small details.