You have to complete your Sinnoh Pokedex by seeing all 210 pokemon. Then go talk to Professor Rowan in his lab and you will get upgraded to your National Dex.

First, you can get two Regigigas on Pokemon Platinum. But to get Regice, Registeel, and Regirock you have to have the event Regigigas to unlock the special caves that Regice, Registeel, and Regirock reside. Also I can tell you the locations of the caves. For Regice it is deep in Mt. Coronet. For Registeel it … Read more

If you have an Action Replay for DS you can use this code and press L+R to activate. Here's the code: 94000130 fcff0000 62101d40 00000000 b2101d40 00000000 00000090 000f423f d2000000 00000000