Flashback episodes were
Thunder Path,
The Sporilla and
Operation S.A.S
At the end of this episode Zelda anounces she has a brand new cryogenic store with brand new monsters but she was still using her old monsters after this episode like
Sram in First Strike,
Lord Tempo in First Strike and Time Warp
and
Yuri in First Strike and Terratomb
In fact she only uses one of her new monsters which is Captain Goat in Jolly Roger One