If Optimus Prime - Battlefield Legend attacks and flips an Espionage and uses it for his effect, can you also add it back to your hand, with the green icon mechanic? Or does the ‘played’ card become in play for the turn, thus, not being able to add it?

In this scenario, you would be able to add Espionage back to your hand.

As of this (FAQ's) writing, these are all the Decepticons that can benefit from his abilities.

If your opponent attacks one of your characters when all of your characters are untapped and you tap your Raider Ravage, Espionage · Saboteur to boost their defense, Raider Ravage does not become the sole valid target for the opponent’s attack due to its tapping, as it is being tapped after the opponent has chosen a defender. See the Official Expanded Rules for further questions on the relevant attack timing.