Answer 1

You can only get Celebi from and event. Unfortunately, all the events with it have passed, so you would have to trade for it. If you have the japanese version of the pokemon colosseum bonus disc, you can get it on a GBA game, then pal park it to gen 4.

Answer 2

See here: http://pokemondb.net/pokebase/6609/how-can-i-get-celebi

Answer 3

no pokemon is not getabel you can use cheat to get it but i dont alow it but in this case i do