you cant
There currently is no glitch that allows you to have every Pokemon without cheating. However, get action replay for Pokemon if you really want to cheat.
Use the GTS and some friends, and be VERY lucky!
no
yes
You have to battle every Pokemon Trainer in Sinnoh.
you had to get alot of them through events or mystery gifts
in every pokemon game you get one master ball before the leauge
There is no code for that, unfortuneatly.
A Pokedex cheat
yes, if you're willing to put it in your action replay DS
The only way that you can et Darkrai without an action replay is to go to a Pokemon event that happens once every six months at places like argos and you get a membership card to get in the inn at canalave city.