You need to beat both games, as in defeat the Elite four in FR, and beat Evice in Colosseum. Then, use a GCN-GBA game link cable for your SP/Gameboy Advance to trade. Phenac City is the only place you can link up once you've done that~
No.
no
ofcource you can
You cannot "trade" pokemon between Pokemon FireRed and Pokemon Pearl. Instead, pokemon from Pokemon FireRed Version can be transferred to Pokemon Pearl via Pal Park.
There is no emerald to trade between firered and emerald you need wireless adapters.
In Pokemon firered you can't, but in Pokemon leafgreen you can get it then trade it to Pokemon firered.
After you have beaten the game. Note: You also need to have beaten the Elite Four in your GBA Pokemon game to trade.
Red, Blue, Yellow, Gold, Silver, and Crystal can trade between themselves. Ruby, Sapphire, Emerald, Firered, and Leafgreen can trade between themselves. Games from list 1 cannot connect with list 2.
The only way you can trade between emerald and firered is by wireless adapters, in emerald you need the national dex and in firered you do as well plus in firered and emerald you need to beat the elite four and in firered you need to deliver the ruby and sapphire to celio at one island once this is all complete you can trade between emerald and firered any Pokemon you want.
you need a special link cable though
You can trade between firered, another leafgreen, ruby, sapphire and emerald also Pokemon colosseum and Pokemon xd gale of darkness.
Pokemon Emerald: Birth Island Pokemon Sapphire: Trade from Pokemon FireRed, LeafGreen, or Emerald. Pokemon Ruby: Trade from Pokemon FireRed, LeafGreen, or Emerald.