Bulbasaur
No, there is not a Pokedex after the National Pokedex in Pokemon Diamond Version.
No all you have to do is SEE the first 150 Pokemon then you shall get the national dex..
you compete the sinnoh dex.
Yes you can but first you need to get national dex!
The first pokemon in the national dex is bulbasaur, which can only be obtained by trading, or by migrating from gameboy.
you cant get every Pokemon be4 you get the national dex
What you have to do is catch all the Pokemon from all the other regions(complete national dex.
=you first have to complete the sinnoh dex,this is not that hard.==however the national dex is,YOU HAVE TO CATCH EVERY POKEMON THERE IS!!!!!!!!!!!!!!== you HAVE to trade and migrate,==hope it helped!==^_^=
First beat the game then get the national dex and then you can go in!
you need to have seen all the Pokemon in the regean first
First get the national dex then beat th elite4
bulbasaur