Buy ActionReplay and use the cheats on that, and it will say that you have all the pokemon, but you really wont.
go and battle every trainer you see. most of them will have Pokemon you haven't seen. but some you'll have to catch and evolve. and some you'll have to migrate or trade from different games.
Yes There Is.
Complete the sinnoh pokédex and get the national one
Not really sure what the question is here, but you can get other master balls from other Pokemon game, like FireRed, LeafGreen, Sapphire, Ruby, Emerald. However, you need to have the national pokedx to open pal park, so that you can transfer the Pokemon over holding the master ball. Or trade on over from diamond.
that would be me
the easiest way that i no of is to just go underground and start digging
No its just the easiest Pokemon to breed with.
use the exp share
The easiest legendary to get is Palkia, just use masterball if you have to.
The easiest way is to use the Poke'Radar.
i recommend the restaurant near lake valor
Get an Action Replay and select 100% Pokemon on pokedex.
The easiest way is just buy a r4.
The great marsh or migrate(easiest to migrate)
yes
You have to see every Pokemon in the sinnoh region.
You need to complete the Pokemon league
From what i know you complete Pokemon diamond and pearl by getting all the gym badges, beating the elite four and completing the pokedex. But im not sure if you have to catch all the Pokemon.