I think the best would be Chimchar. It's final evolution is Infernape. Infernape is very fast and I had mine learn physical and special moves. But the other two starters are very good too. It depends what you like.
You can't unless you trade someone that has one.
You could cheat or soft reset.
You must evolve it from the grass starter.
No, you can't find any starter Pokemon in the wild in any region.
Well, Chimchar is good fro starters in Pokemon, so it would be the best. Next, Turtwig is the medium for okay Pokemon trainers. Piplup is for challenged Pokemon trainers who are well experienced.
You need to trade one from Diamond, Pearl, or Platnium.
luxary
You can't find Registeel in Pokemon Platnium. You just migrate it in Pokemon Ruby, Pokemon Sapphire, and Pokemon Emerald.
There is no 'platnium', but you can find it on wild pokemon.
you cant catch it in platnium but you can trade it
the most wanted in this houshold is Pokemon platnium
It is Pokemon platnium.