Pokemon #134: Finneon.
Pokemon #151: Manaphy.
YES.
fill your pokedex and battle more trainers
Yes you can you have to beat the elite four and then get the national pokedex.
no you can migrate unless you have the national pokedex in Platinum
yes you have to beat the elite four before you can migrate but you must also finish the pokedex so you can get the national pokedex
After you have beaten the elite four and get the national pokedex you go to route 214.
After the Elite 4, you can move on and complete you Pokedex. Also, if you're done that, you will receive the National Pokedex from Professor Rowan if you pay him a visit. You can work on filling that out as well. Of course, this is all optional.
The rare Pokemon which you can get before the Elite Four in Pokemon Platinum are Giratina, Mesprit, Uxie, and Azelf.
To get the National Pokedex, you must have seen all Pokemon from the regional Sinnoh Pokedex after beating the Elite Four and Champion. After doing that, go to Sandgem Town and talk to Professor Rowan in his lab and you will get the National Pokedex.
After seeing all of the Pokemon in the platinum pokedex (250 I think) and beating the elite four. you can get the national pokedex which contains all 493 Pokemon
No. All you have to do is beat the Elite 4.
You can't,you have to trade it,or must've beaten the elite four,finished your pokedex and got the national dex