After you beat the Elite Four go into Cerulean Cave and follow the maze and you WILL see Mewto standing at the end of the maze!!!
fire cave
go through the fire cave beside the cart that takes you up the mountain
there is no diglett cave in Pokemon ruby only in leaf green and fire red
go to the fire cave
go through digletts cave
You Can Go Into This Cave Once You Have Beaten The Pokemon League. Cerulean Cave Is Where Chanseys And Mewto At LVL 70.
use cut on the door then go left then up then rite then down in the holes.
Not that I know of, but there has been talk about the walk through walls cheat in the Altering Cave. www.youtube.com/user/kyogresymbol14
Well..if there is a Pokemon that holds a fire stone...but i found mine in a cave
No mewtwo is there
use cut
North of One Island.