He has Metagross
The least you'd want them to be is Level 50. Since there's another fight directly after him and another Shadow Pokemon (Tyrannitar) I suggest being level 55 at the most. The shadow Absol you get will be very useful and so will the legendary dogs if you have them purified.
yes
tyranitar i think
theres no shadow mightyena on Pokemon xd but there is a shadow pochyena
The final Colosseum is the Deep Colosseum after the Game, Pokemon here are Level 60-65, this is where you can catch the Pokemon you missed from the Admins earlier and a Shadow Shuckle.
Shadow Rush is only a Pokemon XD/Pokemon Colosseum move.
I think its 48 or 49.
You can't level up a Pokemon while it is a shadow Pokemon, but once you purify it, it will regain all the exp. points it would have received when it was a shadow Pokemon.
yes, you can, traded, or purifyed
Shadow Rush is a move learned only by Shadow Pokemon in Colosseum and XD: Gale of Darkness that does 90 base damage (Colosseum)/55 base damage (XD: Gale of Darkness) and causes recoil to the user. It's super effective against all non-Shadow Pokemon.
It's A Shadow Pokemon. A Bodybuilder Has It At The Under Subway And Snagem Hideout.
Here are 2 lists. Serebii has a list of shadow pokemon, while Bulbapedia has the shadow pokemon and evolutions.