Mega Evolution is actually not permitted on the site, since it's simply too OP. We know Mega Evolution can't be triggered outside of battle, but this is an apocalyptic setting; battle is everywhere. It would be possible to have a Mega Evolved pokemon at a nearly constant state, and that overwhelming amount of power tips the scales just a bit too much for the admins' liking. There's also the fact that we can't have it time-based, since a single day in rp can last up to years
in the real world with posting delays, skips, members leaving and new ones replacing them.
So while, yes, you technically can, your creation and hard work would never actually be used.
I'm sorry, but your second question confuses me. Elaborate?