There exists no trick to get a Level 100 Regigigas in Pokemon Diamond, except by manually levelling up the one found in Snowpoint Temple.
you should have.giratina level 100,regigigas level 100,rayquaza level 100,and a kyogre level 100these Pokemon are really good,maby a groudon level 100.
Train your pokemon.
level 100
The highest a pokemon could be is level 100.
Pokemon movie nr. 11, you can only get the lvl. 100 regigigas as a gift while you watched the movie, in Japan. Such an event was once, not anymore. but if you want, you can get the lvl. 100 regigigas from a friend, if someone has it :-)
If you receive Regigigas as an event, it'll be level 100. If you obtain the National Dex and bring Regirock, Registeel, and Regice with you to Snowpoint Temple, it'll appear to be level 1.
Arceus is level 80. If you dont count him then the lv 100 magikarp. If I recall correctly, then you can catch a lv. 1-100 Regigigas
ergfergfs
No, you cannot.
Lv.100 torterra,Lv.100 infernape,Lv.100Empoleon,Lv100 Arceus,Lv.100 Electivire, and Lv.100 Regigigas
You could level your low level Regigigas up to level 100 by giving it EXP. SHARE and then beating the Elite Four a gazillion times, or you could cheat and make Regigigas level 100 when you catch it.
any level up to 100