find all 210 Pokemon on sinnoh pokedex then visit profeser rowan
You have to see all Pokemon Pokemon. But not the ones on nationaldex.
You can fish for a lanturn after you get the nationaldex at route 220 with a super rod.
after you get the nationaldex you go to sadgeom town and surf down
you see him near the spring path which is near Veilstone City
yes yo have to use pal park when there done "constructing" it
After you get the nationaldex you find it in the great marsh
Starly.
No, you have to trade them from Diamond/Pearl or Platinum. You can also get it from a poke walker route called Tree house. (15,000 wats to unlock)
It's not as easy as it was in diamond, there are 250(or something like that)Pokemon in the platinum sinnoh dex. But you just have to SEE the Pokemon, not capture them. First you need to defeat the elite four, you need to see every Pokemon on sinoh region, and nex you go with professor Rowan and he will give it to you. You get it after completing the Pokemon League.
u have to beat the nationaldex
You get the diploma from catching all Pokemon from Nationaldex and Hoenndex.
no