Is the money you obtained from winning the Quran competition, after your cheating in it two years ago and your repentance now, unlawful and must you donate it, or is it permissible for you to use it?

A financial prize obtained through deception is not permissible for the one who takes it, due to their violation of the donor's condition. They must return it to its source. If that is not possible, they should give it in charity or spend it on acts of righteousness.