Make Changes to Digital Game

I have a digital game (php) and there are changes/improvements that need to be made. 1) Front-end needs to change (the front page of the game and how users pay and get their subscription codes that allow them to access the system) 2)Admin Needs to be able to control how long subscriptions are valid and admin needs to be able to issue practice subscription codes for demo of game by potential customers. 3) Some of the problems have incorrect formulas to determine the correct answers 4) Admin needs to be able to easily add questions and change formulas 5) On the game, the user can set the time ("Set The Timer Page") while users work the problem, but the new problem disappears as the view of the stop watch appears. I need the new problem to stay displayed while the timer is counting down. 6) Need to change the image of the girl who is holding the dry erase board showing the formula 7) A few other cosmetic changes are needed to improve the game A copy of game is posted at [login to view URL]