Yes there's 2 ways the long or short way, Long Way: From firered or emerald trade your Pokemon to Pokemon colosseum or Pokemon xd gale of darkness then trade those Pokemon to the other game (i made it seem short but it takes awhile). Short Way: The fastest way is to use Wireless Adapters you can go to either the direct corner's Trade Center or use the Union Room if you feel like it either way you will get your trading done. Yes you have to have Wireless Adapters because the special machine in one island only hooks up to Ruby and Sapphire by Link Cable but the machine does allow trades between Emerald but Wirelessly like i said.
I belive you can. All you have to do is give the ruby and sappire to Celio(leaf green/ fire red)after you beat the elite 4, and obtain the national dex. For emerald, just beat the elite 4 and obtain the national dex.
Pokemon Emerald: Birth Island Pokemon Sapphire: Trade from Pokemon FireRed, LeafGreen, or Emerald. Pokemon Ruby: Trade from Pokemon FireRed, LeafGreen, or Emerald.
You trade from Pokemon FireRed/LeafGreen
Trade from FireRed/LeafGreen
Trade from FireRed or LeafGreen.
Trade from FireRed or LeafGreen.
Trade from Firered or Leafgreen.
it's not in emerald,you have to trade from leafgreen or firered
Trade a charmander from firered or leafgreen to emerald.
you need to trade from Pokemon leafgreen or firered
You have to trade from Firered, Leafgreen or Pokemon XD.
To get Seel in Pokemon Emerald you must trade for one from Pokemon FireRed or LeafGreen. Seel can easily be found in the Seafoam Islands on Pokemon FireRed and LeafGreen.
Trade from FireRed, LeafGreen or Pokemon colosseum.