Professor Oak is't in Pokemon Diamond . o.o Not that I remember lol I beat the game along time ago but I don't remember Professor Oak ever being in it since it's Sinnoh .
professor oak only appears in diamond but if you want to meet him try sapphire version
You can't battle him. But you can find him in eterna city after you got the pokedex upgrade off him (he is in the empty house).
you cant
mr. Pokemon house
Pallet town in Kanto
He won't. You only get one.
You can NOT battle Professor Oak in Pokemon FireRed Version, even with an Action Replay
no such thing
Pokemon diamond
Pokemon diamond Pokemon diamond Pokemon diamond
you cant be a Pokemon in Pokemon diamond
She is not in Pokemon diamond.