Using action replay get the capture trainer Pokemon cheat and then an ace trainer near stark mtn has one
You can only get seviper by using the action replay cheat code or trading it from diamond, pearl or even platinum.
You don't, so sorry and you wont get on in there but if you do...
In Sapphire and Emerald, you can find Seviper at Route 114. In Diamond, Pearl, and Platinum, Route 208(Sapphire has to be in the GBA slot.).
There is no trainer in platinum that is willing to trade a munchlax.
Sorry but there isn't a trainer with a bagon in platinum.
you can find the trainer with the misdreavus in platinum in hearthome city i believe
no one no trainer has a kingdra in Pokemon platinum exept for me :P
The trainer in victory road
A trainer on iron island has hippotas
A Trainer on route 220
A trainer has it in their party on route 221.