I'm not sure how this game works (yet, My charmander is only lvl 11 :P). But can't I keep using my same pokémon? And level those up?
Or how do these different zones work? You lose all your pokémon when you enter a new zone?
When you beat Kanto's Elite 4 and choose to start Johto, all your Kanto Pokemon are locked in your PC until you get all 8 badges of the new region. So, you're pretty much forced to use the new Pokemon. Of course after you finish all 3 regions you can use any Pokemon you want.
And the first generation has some (obviously not all) of the strongest Pokemon, so you will be good to go.
Is there any place to see the pokémon that are considered strong?
Planning on making a team like: Charizard, poliwrath, primeape (or hitmonlee/chan), nidoking - Haven't figured out the rest yet