Furthermore, is it possible to go back down to v2.00-final from v3 as well, or are we stuck at v3 now?
You can go back to v2 just by applying a v2 upgrade file -- except that, if you've added or removed any music with v3, you'll need to force a database rebuild after installing v2 (e.g. by deleting /empeg/var/tags). The v3 player doesn't destroy the v2 database, but it doesn't keep it up-to-date either.

Peter