By new Pokemon do you mean starting a new game. You just start a new game them.
Swinub is not in Pokemon LeafGreen.:new person here: you can get swinub at ice cave on four ilsand
Yes you can trade leafgreen version Pokemon to another leafgreen version.
press new game
Not in Pokemon leafgreen only in Pokemon Firered never ever in Pokemon leafgreen And in Pokemon firered it is rare in power plant not available in Pokemon leafgreen?
rainbow pass
If i were you i would choose a bulbasaur because it is great for new trainers.
you should go to gamestop
HelloSorry to say but you cant trade Pokemon from pearl to leafgreen but you can migrate Pokemon from leafgreen to pearl via the pal park
On Pokemon Pearl's title screen, if the Pokemon LeafGreen game is in the GBA slot, click on "Transfer From LeafGreen" and you can choose six Pokemon from LeafGreen to transfer to Pearl, but be careful-you can't trade them back.
Manaphy is a legendary water type of Pokemon. It is not possible to get this Pokemon in the game Pokemon LeafGreen.
You can't catch ralts on Pokemon leafgreen or firered because ralts is a new hoen Pokemon so it won't be available in the kanto games. Hope this helps, The Dudiest Dude On The Planet
Keep capturing pokemons, and train your pokemons so they evolve and become a new, similar pokemon.