yes you can catch all the legendaries you dont have to pick one you can get all of them
50 Floors
Sky Stairway is A Pokemon explorers of time/darkness dungeon
Go to a walk through page!
http://www.upokecenter.com/games/dungeon2/guides/wondermail.php look here
go 2 the top of sky tower. requaza will be there
In Pokemon Sky, rayquaza is at the 50th floor at Sky Stairway
it is 50 floors and at the end you fight rayquaza if your starter is your team leader he will ask to join after you beat him
in Pokemon sky you get a challenge letter from mewtwo on sky stairway f49(if not found keep waiting and go to spinda cafe and eventully you'll get sky stairway) and defeat him and He will join your team.
Mew is on Floor 30.
Use the Nitenndo WFC to recieve wonder mail, click explopre Sky Stairway PS you can only take this Job if you have rescued Scizor From frosslass
50 floors
49 and the summit boss rayquaza. pokemonmaster10