1-Is the retail edition available for pre-order? Haven't seen it on Amazon.
2-Will the code be for GOG? I pre-ordered the retail version of Hearts of Stone on amazon and the code was for GOG, this is going to be the same, right?

buying it outside of gog is a slight risk that it may not,ask a trusted vender with money back if it doesn't work.

There's the limited edition on GOG? I don't see it, i saw the standard one.

1. Can't speak for Amazon but local online stores have it lsted here. It shouldn't be too far away from being listed.
2. Yes, it will be the same; GOG download code and two physical gwent decks (different to Hearts of Stone decks).

The limited edition part is just the gwent decks. There's no limited edition on GOG.

I think it will be a wait for Limited Editions and Special Editions but they will come as sure as the sun rises each day.