Deoxys is found on birth island which is unaccessible due to a Nintendo event that already passed for the aurora ticket sorry you can't get deoxys unless a friend has one.
You cant.
only way is to trade from another Pokemon game
without gameshark or action replay, NO
yes you can trade pokemon leafgreen pokemon to pokemon emerald version same as pokemon fire.
you cant because leafgreen is an older game then Pokemon pearl plus its a gameboy advance game.
Manaphy is a legendary water type of Pokemon. It is not possible to get this Pokemon in the game Pokemon LeafGreen.
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?
Level them up
Not in the game.
you cannot clone Pokemon in firered/leafgreen. the only gba game you can nlone in is emerald.
Pokemon colosseum is another Pokemon game.
You can't get charmander Without migrating one from your leafgreen/firered GBA game.