Right im planning to jailbreak my IPhone 4 (4.2.1) but wanted to ask a few questions first. What software should I use to do it? I looked on youtube and google and greenpois0n seems to be the best, if so can you send me a link to download the software. Do I need to backup my Iphone at all before doing it? I read about this somewhere and I dont know where, so no nothing about it so thought it was worth asking if it needs doing, why and how. Lastly, obviously jailbreaking voids your Apple warranty, but say if something went wrong with my phone and I needed to claim on the warranty when its jailbroken, could I still claim on my warranty if I just restore it to factory settings on iTunes? Because obviously then the phone has been wiped? I live in the UK if its worth mentioning for whatever reason.