User blog comment:Aftenshnoshnikr/Attack On Titan's Tribute Game/@comment-101.176.100.157-20140922024134/@comment-98.112.170.77-20141006001148

You can only change on Forest II and Forest III.

The charge-time before you can change is 2 minutes.

On PvP maps (maps that allow player titans), Eren has his variant of Petra's special.