I noticed that opponents at different rounds use different movesets. They have to run out of new movesets eventually, right? Please don't question my curiosity.
Edit: I already have partial answers for the Generation 4 Battle Tower, Battle Maison, and Battle Tree. I'm only missing information for the RSE Battle Tower and the Battle Subway. Thanks to SadisticMystic for giving such a good partial answer and sorry for having to convert your answer to a comment.