The Classic platform is one platform, and one price for this. So you purchase the classic platform and get all the apps on that platform. There is no way In which to purchase only downloads
There is only one points system. For what you are describing, it would essentially be 2 points systems
There isnt. The leaderboard is actually not based on posts either. The leaderboard is based on a users reputation, which is something given in the form of reactions to content