Unfortunately, you can't catch a Red Gyardos is Pokemon diamond, but you can catch one in Pokemon Heart Gold or Soul Silver. It'll be at Lake of Rage.
You can't catch one.You need to trade it from Pokemon Diamond/Pearl/Platinum version
Darkrai is a dark type of Pokemon. You can catch one in Pokemon Diamond version on Newmoon Island but you need a membership card.
You cannot catch a slowpoke,slowbro or slowking on diamond version. You can on Pokemon pearl version though.
5
You are not able to catch the regis in Diamond. You can catch them in the Game Boy Advance version of Pokemon Emerald.
use ultra balls
You can't yet.
You need to trade or migrate it.
Sorry to say, but no, you cannot catch a Palkia on Diamond version. You catch a Dialga on diamond, and Palkia on pearl. You would have to trade to get one.
You catch it at the top of snow point city.
Misdreavus cannot be obtained on Pokemon Diamond, so you must trade one from Pokemon Pearl.
use poke balls on it