Poliwrath
it is omastar
You have to see them
Yes.
its bulbasaur, and you need to migrate it from fire red or leaf green.
150 Pokemon for fire red and leaf green (not including legedaries or hoen and johto Pokemon)
You can trade from firered version on second floor of the Pokemon center after you get the pokedex.
gotta catch it first
You have to catch at least 60 Pokemon and you have to beat the elite four including your rival
He should give you a pokedex.
You can link and trade Pokemon with Sapphire and Emerald Versions. If you want a national pokedex, trade with leaf green version
cant YOU CAN MIGRATE IT FROM POKEMON FIRE RED OR LEAF GREEN AND GO TO THE PAL PARK AFTER GETTING THE NATIONAL POKEDEX
You can't catch Charmander in Pokemon Diamond. You have to import it from Leaf Green or Fire Red.