I have downloaded this game and when I launched it, opposite of "full" installer download there, the main menu tells me that I play a demo version. Are there any limitations? And if yes, is there any place where we can buy the full version?

I have the same question, and I tried to contact them via mail, hope they answer, I really want to play this game again, I love it
I use to own a key back in the day, but I lost it