Just got a brand new 32gb iphone 3gs from apple on warranty because of problems with my old phone. I haven't put my sim in yet. Just comes up with the screen that says "install a sim card to activate". I have an att sim card to use if need be. I want to jailbreak and unlock this phone. How do I see what bootrom I have? What steps do I take to jailbreak with ios4? Or should I stick with 3.1.3? I have a mac. Thank you.