you don have to
Once you deliver the ruby and sapphire to celio the machine will be in operation this means you can go upstairs in any Pokemon center go to the trade center and trade between ruby, sapphire and emerald version.
Simply trade between ruby, sapphire and emerald, remember to trade with emerald you need wireless adapters.
have a gba cable,go to the top floor,go to third counter,push "trade center" and have someone else with Pokemon Emerald,Ruby,Sapphire then trade. "but will save before entering."
If you want to fill your pokedex, you must trade between Ruby and Emerald to gain the Pokemon that are not in Sapphire.
You can do this after you find the Ruby and the Sapphire for Celio in Pokemon FireRed. then you can trade with Ruby, Sapphire and Emerald.
You can either use GBA link cables to trade between ruby and emerald via the upstairs room in the Pokemon center or you can use a GBA to GCN cable to trade with colosseum and xd gale of darkness.
get a cable or link that connects into two different gameboys, go to the Pokemon center(up stairs) and go to cable club
Ruby/Sapphire/Leaf Green/Fire Red/and i think Emerald. if not, trade from emerald to Ruby/Sapphire, and from ruby/sapphire to leaf green. You need to have the Sapphire and Ruby before you trade. you get these after the elite four.
You cannot get Kyogre on Ruby. You either have to trade it with someone who has Sapphire or emerald, or get sapphire or emerald. Sorry...
only when you get the national dex on Sapphire version
You can not get Meditite in Emerald. You must trade from Ruby or Sapphire.
Meditite is not available on Emerald. Trade from Ruby/Sapphire.