Add New Features and Bugs Fix on a PHP site

I can only pay up to $50 for this project. Feel free to PM me if you need clarification. Thank you! New feature: 1.) My current site has only 2 usergroup and I want to add another 6. When user's meet certain requirements, his usergroup should automatically change. (More info will be provided) 2.) Add sort by function to all categories and sub-categories(Title, date, most popular and rating). Bug Fix: 1.) My site has problem in detecting username when user's are accessing through cell phone. I'm not sure what the problem is. You help me to solve it. 2.) The last one is URL problem. URL wouldn't remove from site after name changed. (More info will be provided) I don't pay upfront for my project. But full payment will be transferred into escrow and release once it has been completed to my satisfaction. Winner can expect more job in future as there's more bigger upgrades needed on this site. And I also expect you to be able to reply me within a day. Thank you for bidding! Sincerely, Larry