Add Some New Feature including Bug Fix and Layout Change on PHP Site

I can only pay up to $50 for this project. Rest assure more project will be followed if I like your work. Please read carefully and understand the scope of project, feel free to PM me if you need clarification: 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 had problem in detecting username when user is accessing through cell phone. I don't what the problem is. You help me to solve it. 2.) Some code problem that couldn't detect certain allowed files. (More info will be provided) 3.) 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. Thank you for bidding!