Also, i should mention, if playing with sideboard and you or your opponent use EC first game, you have to play the same deck in replay, as it wold still be game 1.
Example: Game 1: you start with a 33 card sideboard. Opponent gets awful draw and uses EC to replay. You must play your 33 card deck in replay; you can not remove 3 cards.
I suppose this also applies to other games than the first one?
Yes. So, in other games, if sideboard has already removed certain cards, in case of replay, the same cards are left out.