You actually have to reddem it as a prize at the radio tower/or after u get 8 johto region bages prof.elm will call u go to new bark town go into prof.elm's lab and he will give u a master ball
professor elm gives it to you
after you beat Clair elm wiil call u and will give you the masterball
train up your Pokemon and woop red's a**
after u beet all gyms in johto region.
you get it when you beat all the johto badges in the game and prof. oak will call you and give you a masterball p.s never let a sister use your pokemon games if she doesn't know pokemon and you have a masterball hope this helps!
in Pokemon soulsilver you get a masterball after you get al the gym badges from professor oak
on any legendary(just that it should be a strong or rare legendary)
you get 1 after you beat the 8th gym and go to dragons den for a test.
Not unless you attach it to one of your gen. 3 Pokemon and migrate it ( if you still have it and didn't use it)
You probally want to use it on mewtwo because it is level 70
get all 8 gym badges and profeser elm will give you a masterball and you can find lugia in the whirl islands and you need a silver wing
you cant find celebi in soulsilver