I have an iPhone 3G running iOS 3.1.3 and I had some questions about jailbreaking. 1. I wanted to jailbreak my iPhone for biteSMS and iPhoneDelivery. I was wondering if those apps still support the 3.1.3 firmware. 2. If I were to only install those apps upon jailbreaking, what would be the impact on my phone's performance? All I do is text, call, and sometimes use Facebook. 3. If I jailbroke my iPhone, and later down the road I decided I wanted to take it off, would I still be able to restore my iPhone to 3.1.3 using iTune's "restore from backup" feature or would I be forced to restore and update to 4.2.1? Thank you for your help.