first buy as many ultra balls you can and battle Mewtwo. Once his hp is low start using the ultra balls (just keep trying until you got him)
no you cant but you can catch mewtwo in a cave in cerulean
You can't catch giratina in soul silver, you can only catch him in diamond, pearl, or platinum.
you have to get it from Pokemon platinum or diamond
jhoto and kanto regien Pokemon
you get it in cian iwood from a guy
win a battle against nurse joy and she'll give you a egg!
hes at the route were you first meet misty after you chase him around.
You'll need to evolve Tyrogue when Defense is higher than Attack.
You cant catch one, but you can get one by a WiFi event or traded by a friend. BTW the event has already Finished.
you dont make poffins in soul sliver
There Isn't
read the wall and catch all the unknowns