i saw on a site about the lost world playstation game platinum edition ,is it like the special edition with longer live,new Rex levels,etc ?

Platinum edition generally means that it was a best selling game at one point and therefore is available at a discount price.

So it should be the original Lost World for a reduced prize. If you don´t have the game you should pick it up, it´s really worth it, if only for the Rex rampage levels.