That isn't true, but it's recommended since the elite four uses nearly all types of pokemon.
No you don't need it to finish your Pokemon game
trading a Pokemon from a DS game and a GBA game? You cant because they are different types of games
finish of game xD if you completed the pokedex clear
you finish the game and then migrate them
finish the game
you have it!
No, you don't have to finish any Pokeathelon to continue the game.
No, there isn't. The legendary Pokemon for emerald is raquaza and that's it. when you finish the Pokemon league, you finish the game.
you have to finish the game then do a mystery misson
it does,if you complete its courses.
when you finish the game ursaring will tell you the luminous spring is different and then when you go you can evolve rabidrabit
all game yes but when you have all the Pokemon is not possible