You have to collect all Pokemon, of course. You have to Migrate Pokemon/ Trade from others to get all 3rd, 2nd and 1st Generation Pokemon.
complete the normal pokedex
yes
NOTHING
Yes
you need to find 210 Pokemon to complete the pokedex
First complete the sinnoh pokedex, 210 Pokemon
you have to go to Professor Rowan.
There is only one legitimate way to complete the Sinnoh Pokedex. To complete the Sinnoh Pokedex you must trade for the missing Pokemon with Pokemon Diamond, Pearl or Platinum.
you have to beat the Pokemon champion and later on in the game you will complete it
Just go to Pokemon platinum central and click on pokedex and it shows you where to battle all the Pokemon in sinnoh.
use complete pokedex cheat !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!l +r+select
Battle every trainer you see