You can't. You have to catch them in the hoenn region and then transfer them via pal park. Then, with them in your party, you can go to snowpoint temple and catch regigigas. by using action replay for ds but it will take time to do it though
No.
After you get all three Reggies (Regice, Registeel and Regirock) there is not much else to do with them seeing as you most likely caught them on the pokemon sapphire/ruby/emerald game. For either Pokemon diamond, pearl or platinum you can trade the three reggies onto it and go to the sacred chamber place which is the town below the snowpoint city gym and with all three reggies in your inventory you can unlock an entrance which leads to Regigas (sorry if spelt wrong been a while since played) it is very powerful and is level 70.
Trade with Pal Park.
yes Regies:use the Pokemon modifier cheat witch you can find on this site
In one of the three lakes.
kyogre, groudon, raquaza, jarachi (I think), deoxys (I think), latios, latias, the three reggies (regigigas couldn't be caught) and some more. I think.
It's not possible to catch Regirock in Diamond. It's possible to catch the three Regi's in Platinum, when you've received the event Regigigas, but not in Diamond. To get it i Diamond, trade with Platinum, or migrate from either Ruby, Sapphire or Emerald.
yes if u got the nat. pokedex 1in mt corenet,1 in a island , 1 behind the leugue,and 1 in snowpointtemple.put 1st three in party and go to the temple.then redgigigas will be awakened!
you have to catch Palkia(in pearl)orDialga(in diamond)
you go to three lakes
You go to the three caves and catch them.
Yes, you need all three. So dust off your copy of ruby/sapphire/emerald and get working.