Question

Do we get the National Dex even before compeleting the game.Torchic is not in the Dex but we get it.Why?

Answer 1

I have completed the game and you get the national dex when you go see the Pokemon Professor post-game at the train station.

Answer 2

You get the National Dex later ingame, but it still is possible to have Pokemon from another region in your game. FOr example I had a few Pokemon that where not int eh Unova dex in Black2, and there merely have ??? as their dex number. Th reason you can still get them is because you dex does nto govern what you can have, it just gives info on the Pokemon entries it has.