adding features and some developments. I need experieced one

My website [login to view URL] is a daily Quiz site. Currently questions set in a day appears to all. I'm facing some problems as people are opening multiple accounts an answering more then once which is against my TOS. (1)Now I want to randomize the questions. I want the script to be written in a way so That I can input let say 20 (I want this to be according to my choice) Questions and the user will get 4 questions to answer. 4 questions will be rotated randomly from those 20 questions. also I want my system to detect the Ip and make sure that same questions are not displayed simultaneously. I assume that there will be about 20X4=80 variations if the question is random ( I guess so). (2)Also I want Ip detector. so I can see from where people are registering/logging in/ etc. Also I want the ability to suspend the ip for a certain period. These are the two major works. there could be 9-10 more small works that I will tell you when you are working. Please bid as low as possible.