South of Rock Cave.
16
the powerplant
In Cerulean City Gym.Superoo10
u can find her in saffron city
Fight the galactic grunt and he'll give it to u
part of team rocket
you buy it .
dowsing machine
surf under mauville city. you have to go under the cycle path. You then enter a cave with the generator at the end of the cave
no you can trade soulsilver pokemon to black
Mewtwo is in the deepest part of cerulean cave
he is not in Pokemon soulsilver or Pokemon heartgold