Hello, I have a jb 3gs running 3.1.3. Just wanted to get some advice. I was thinking of buying an iPhone 4. One thing I wondered, can I still use categories if I bought an iPhone 4, or updated my 3gs to 4.0. I don't like the folder setup of os 4.0? Also if I stay at 3.1.3 should I update my apps in cydia, and the app store? I wondered if I update my apps would they still be compatible with my old operating system? Any info would be appreciated.