yes you can. You can either migrate from ruby or saphire. Or go on the wwwwtu ( world wide wifi trading unit).
transfer from emerald
You could migrate it from another GBA game, but otherwise it is impossible without the Emerald Cartridge.
You can't find Rayquaza it in pokemon diamond, pearl, and platinum. You just migrate it in Pokemon Emerald, ruby and saphirer
You cannot clone Pokemon and items on diamond and pearl and platinum, but you can in emerald!
Trading from Emerald is your most probable option.
after you have the national dex, you can find it on route 206.
You can't without trading, migrating or, cheats
you need Pokemon emerald pass all rare candies
You need an action replay. Or you beat emerald and migrate the chickorita
well i dont know about diamond or pearl but there is a emerald cloning cheat if that helps
You have to upload it from FireRed, LeafGreen, Ruby, Sapphire, or Emerald.
i know how to get nearly every Pokemon without a cheating device. do you know how to get Deoxis on emerald Or is there a way to get Darkrai on diamond without cheats?