Is it legal to give fake info on Prize Rebel offers

Well, it is not something about legal/illegal. If the Prizerebel staff catches you putting fake info, they would just suspend your account. I recommend you put your real info, because I did, and they didn't mail me anything, but only rarely, spam, and just don't answer the phone when they call you
the offers are jacked up cuz only half of them even give points when completed but try to use fake information for your offers but to claim the prize you wanna buy with the points you need real info

If you sign-up for prize rebel use real info but on the offers use fake info unless you want things sent to your house or advertisers calling your phone
Use something like robo form and fill it with fake information. It wil fill out each offer with the same fake information so they wont know the difference. Make sure that all the stuff makes sense such as zip code, city, address, area code, otherwise some sites will figure it out.