Mew is not in in Pokemon SoulSilver. There was a Mew event however that has ended on February the 11th. You can still catch a Mewtwo in Cerulean Cave at level 70.
u cant
You can't.
you have to get from the wfc center
You can't.
no but you can if you have cheats
no
you cant.someone has to trade it to you
GeT mew
Yes mew two is on soul silver you just need to look in cereleun cave
Mewtwo is in cerulean cave, and you can only get Mew through an event.
mystery gift
you cant you have to trade