rotom(legendary)
no.
478 is the Pokemon froslass which is right before rotom on the national pokedex. and 485 is the Pokemon heatran which is right after palkia on the national pokedex.
210 some are really hard
Im not positive that you can get rotom before the national pokedex but in the old chateau. In one of the rooms he is in the TV
Yes. The part of the story when you can catch Dialga and Palkia is not unlocked until you get the National Pokedex.
Absol is the Pokemon before Giratina. Absol's number in the pokedex is 209 and Giratina's number is 210. This is the one in the Pokemon platinum POKEDEX.
every pokemon from that game and generations before
You have to complete the Sinnoh pokedex before haveing the national pokedex.
Rotom does.
no
in Veilstone I think, a guy will give you a Porygon for free it should be in the 20's
for platinum, diamond, and pearl versions you must see all 210 of sinnohs pokemon. this takes forever. i got 2 palkias, and 2 giratinas before i did this on platinum.