Keep on battling in battle zone and get Bp then buy rare candies with BP

Eterna forest is in the sinnoh region it is not in soul silver or heart gold as they are in the kanto and johto region

Primal dialga is from mystry dugeon explorers of darkness/light it is not available on the main series shadow lugia is in XD gale of darkness but must be purified before transfering to gba games so it turns into a normal lugia

You cannot transfer shadow lugia from XD gale of darkness because it has to be purified before transfer and when it gets purified it becomes a normal lugia

You don't need a cheat take shaymin to flower shop for gracidea flower and use it on shaymin in the day time

T is possible but you have to use a R4 Card and put the game and save onto it then if you have two ds's you can trade normally