You can find celebi in the solaceon ruins. First go to the room where you get the four items, read the inscription, and battle 99 unknowns and the 100 battle will be celebi. WARNING: I don't know if this works because I never tried it but my friend did it and showed me the celebi and it came from the solaceon ruins.
no,you can't
You need to wight for an even to get celebi at Game Stop.
you should have the mystery gift and mystic ticket to get access to the island's 8 and 9, you will find a lot of rare Pokemon there
You get it in a trade.
You can't
Don't know sorry...
Yes,but only with a g.s.ball.
it's completely impossible
You cant...You must get it off of Gale of Darkness
The only way I know is Action Replay/ Gameshark
Ash is not in platinum..
You cannot find Lugia in Pokémon Platinum.