Is the money earned from a competition based on predicting football match results, with a cost for participation and substitutions, considered permissible (halal) or impermissible (haram), and what are the implications of that?

The competition is forbidden gambling, and you must repent sincerely to Allah. The prize money is ill-gotten gains that must be spent on good causes and for the benefit of Muslims, such as orphanages and hospitals. This money is not considered charity because it is not rightfully yours. However, you will be rewarded for repenting from it and avoiding what is unlawful.