can you backwards patch?

[Rodent]

I have a tony hawk 3 that I am trying to crack so that I can use it, this is the fist time Ive done this so I have no clue what im doing.

I patched ntsc-pal, but what does that do, and can you undo it?

and what are ntsc and pal?

can someone give me directions so it works on a U.S playstation?