No you don't have to. But if you want every Pokemon you must.
In Pokemon firered you can't, but in Pokemon leafgreen you can get it then trade it to Pokemon firered.
Pokemon Emerald: Birth Island Pokemon Sapphire: Trade from Pokemon FireRed, LeafGreen, or Emerald. Pokemon Ruby: Trade from Pokemon FireRed, LeafGreen, or Emerald.
no you can't but you can migrate in into diamond and then trade it.
trade trade trade
You have to trade it , and it will evolve on the trade ,
Catch, trade, and battle Pokemon
No.
you have to trade
you can if you trade
Bellsprout has to be found wild, in leafgreen, you need to trade from Leafgreen for Pokemon.
no you can only trade using a game boy to a game boy with the link cable.
Use wireless adapters.