Your best bet would probably be torchic or any of it's evolutions. But if you decided to go with another starter I would probably go with vulpix and evolve in to ninetales it when you have a moveset you like.
the best fire Pokemon in pearl version is chimchar ,monferno , and infernapeHeatron is also a good fire Pokemon
electric,fire and rock
A fire and a fighting type Pokemon is good against steel.
depends how you use it, and what for. If, for instance, it was a dive ball and you used it on a fire pokemon, it would be crap.
you have to level it up with a good level of happiness thunderstone works in a different game
Sapphire is better, but yes, emerald is good.
you have to suck everyone's ass good,luck
depends on moves OR you could probably go for evolution on torchic and also its about levels but the types are good your good against water, grass but get a water or rock type on fire
No, not unless you have obtained the Aurora Ticket from a Nintendo Event and captured Deoxys in Fire Red, Leaf Green, or Emerald. You can also obtain an Aurora Ticket using a cheat code, but that is not good way to get it. If you have captured Deoxys on Fire Red, Leaf Green, or Emerald, you can migrate it to the Pal Park on your Pearl version.
Snorlax
you don't really get oak's rare Pokemon but you can trade with friends. good luck Pokemon trainer ;P
All the 150 Kanto Pokemon exist there as well as a good bunch of Pokemon from Gen 2 and 3. You can't get all of the Pokemon without trading with somebody with Pokemon Emerald.