Are there one-time pokemon I have to choose between in White 2

I recently bought White 2 used, and the previous owner had made it to the Elite Four. Other than the starter, are there any Pokemon they might have chosen over another (and so I should attempt to trade that to another player and then trade back once I start anew)? A similar scenario would be the Mount Moon fossils in Red and Blue; one can only get both in the same playthrough via trading with another player.