From Diamond/Pearl: Simply trade them from your old game.
From Ruby/Saphire/Emerald/FireRed/LeafGreen: You'll need to earn the national pokedex by seeing all the Poekmon in Sinnoh (usually by battling everyone), then talking to Professor Rowan.
migrate from emerald
Migrate it over from your Emerald game to Pal Park.
you put FireRed at the bottom of your DS. Then if you have Pokemon Diamond,Pearl or Platnum insert those into your DS and where it shows where your saved game go down a little bit and it should say "Migrate From FireRed."
Pokemon Platnum comes out on March 22, 2009 in the U.S.A.
Yes.
you need to get a azureflute
TURTWIG
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with an action replay
The Hall Of Origin
You have to beat dawn in a Pokemon battle.
You can't get rayquaza in platinum you must migrate it from ruby, sapphire or emerald.