You don't get the National dex in Generation I since there is only one generation of Pokemon. Once you fill you Pokedex, you can go to Celadon City, and go to the Celadon Mansion/Condominiums (Giant building next to the Pokecenter). Go up to the second or third floor, and talk to the Game Freak workers. You will receive a Diploma for completing your Pokedex. After that, if you have already beaten the Elite Four, you've pretty much conquered the game.
im pretty sure u get a national pokedex (national dex)
Complete the Unova pokedex (after that coplete the national pokedex)
you complete the national pokedex
You go outside...
pokedex or National
oak will thank you on the PC that is it what a blow out
If you complete the national pokedex, go to visit Prof. Oak and he will give you a ticket to a place called foggy valley. You have to get a ticket because it is also an island.
If you complete the pokedex you can get a diploma from game freak in the celadon mansion in celadon city and you can now say to everyone you did it!
You get the national pokedex and a jhoto starter.
You would have to have no life toactually achieve that. Otherwise, good luck with that(:
Do the aftergame stuff
There is an Action Repley cheat for it that will automatically complete your Poke'dex that gives you the info that you would if you caught them. When you get the National Dex it will automatically complete the rest of your Poke'dex. A Poke'ball icon will appear next to all the Pokemon as if you have caught them. Hope that was enough Get info even on something like this :>