Go to professor Rowan's place in Sandgem town and talk to him. Then Professor Oak comes and gives you the national pokedex.
in the sinnoh pokedex dusclops, in national pokedex aipom
in the sinnoh reigon chatot in the national exeggcute
Its Phione in Pokemon Platinum, You can get it by breeding a Manaphy and a Ditto Actually; Rotom comes after Manaphy in the Platinum pokedex. Kthnx. http://pokemon.marriland.com/platinum/pokedex/list/sinnoh/ Rotom comes after manaphy in the platinum pokedex phione can be made by breeding a manaphy and a ditto but he's actuelly not in the platinum pokedex :D
http://www.serebii.net/platinum/sinnohdex.shtml this website has the entire sinnoh pokedex ign.com also has a pokedex
Swinub
in sinnoh 210
Just go to Pokemon platinum central and click on pokedex and it shows you where to battle all the Pokemon in sinnoh.
Swinub is #203 in the Sinnoh Dex in Pokémon Platinum.
Porygon
Pokemon Platinum has two different Pokedexes: the Sinnoh dex and the National Pokedex. In the Sinnoh dex, #152 is Rotom. In the National Pokedex, it's Chikorita.
Manaphy
Picachu
Rotom
Porygon
in the sinnoh pokedex dusclops, in national pokedex aipom
you get the sinnoh pokedex from professor Rowan afteyou battle the starly with one of the Pokemon in the bag and say yes to the professor and you get the Pokemon and the pokedex.
First complete the sinnoh pokedex, 210 Pokemon