you cant
yes
no
dungeon leader can be any Pokemon you recruit. you will be able to change leading Pokemon after you graduate .
Yes
After you beat the game, you will have the power to change the leader at Chimecho's Assembly. You can not change the leader in a dungeon, though.
you can't (I think)
No.
You can't.
Yes but after you complete the game. Including darkrai.
you can't sorry man, but it ain't gona happen!
you have to beat rayquaza to start evolving and having different leader pokemons.
It depends on which Mystery Dungeon. the first one, yes you can evolve and go on, the second, you can't evolve at all, but if you have an action replay you can change your hero Pokemon into any Pokemon you want (you can do the same with the partner Pokemon, unfortunately, you can only change in dungeons.)