Research VS. Exile

[Agrus Kos, Enforcer of Truth]

Exile "removes from the game" so could {Research//Development} pull them back or is the exile zone (as it was changed to, instead of removing from the game) still part of the game?

[Keyeto]

According to tournament rules, you can only pull things in that are in your sideboard.  So no.

For tournament, its the sideboard. Otherwise, its any card from your collection.

Either way, you cannot get something back from exile this way. An exiled card is still in one of the game's zones (exile zone) and is considered "in the game" as far as these type of effects are concerned.

[Agrus Kos, Enforcer of Truth]

If that is only tournament rules, could you do it in a casual game?

[Mattao19]

If that is only tournament rules, could you do it in a casual game?

Well in casual it's up to you and your opponent bc well there's no set casual rules right. But if it's casual and you have another copy of the exiled cards just use that