just don't cheat it's that simple play fair or Pokemon is no fun.
There Is A Pokemon Diamond Walkthrough If U Go To Pokemon .Marriland.com
just search google for Pokemon diamond walkthrough
You Can't
you can not download it.
Serebii.net is usually a good place to start but for an actual walkthrough just Google Pokemon diamond and pearl walkthrough and you will get multiple results
NO.
capture the legendary and train your Pokemon
no
you have to buy it
Go on to Google and put in Pokemon diamond walkthrough. it gives you a step by step guide and shows where items are and what they are!
You can't download Pokemon diamond and pearl, it's illegal.Better, you must buy it. :)
You actually cant physically catch a rayquazza in diamond or pearl. If you have diamond or pearl and you want a rayquazza you need to get pokemon emerald capture it on there and then migrate it onto your peral or diamond game. Cheers boiz and gyrls.