Just getting 3gs with 3.1.3, new bootrom now-questions
I just bought a 3gs on eBay. I have been reading the forums etc, but want to confirm my understandings and have a few questions about jailbreaking, unlocking and my options before I jailbreak/unlock my phone.
The seller wiped the phone a few days ago and declined the 4.0 update, leaving it on 3.1.3 (which I want to keep). It has modem firmware 05.12.01 and serial number 88011xxxxxx (manufactured 11th week this year). The phone was a warranty replacement and is almost new. So I understand this means I have the new bootrom precluding use of pwnagetool (I want to avoid a tethered jailbreak). The seller says he connected to iTunes and moved past the "Connect to itunes state" so it can be run as an ipod right now without a sim and the settings can be viewed.
1) I understand it is OK to connect the phone to my iTunes without limiting my options further, as long as I do not update the firmware, right?
2) So, my only option for jailbreak and unlock (and stay on 3.1.3) would Sprit followed by ultrasn0w, right?
3) Regarding Sprit, should I just follow the directions, but not worry about putting an AT&T sim card in, since it is already activated? Would running Spirit with no sim be OK?
4) I understand I do not have to load an iOS firmware at all during jailbreaking and unlocking with spirit/unltrasn0w and therefore do not need my SHSH file for 3.1.3, right? And if I save my SHSH in cydia on unlocking, I will get one for iOS 4, not for iOS 3.1.3, right? From what I am reading, it seems I cannot restore a copy of 3.1.3 on top of the existing 3.1.3 to totally reset the phone? So, I wonder how my seller was able to wipe his user data (after iOS 4 came out)? Or is there a way to put 3.1.3 on top of 3.1.3 if I ever want a clean start? Or can I extract the current SHSH from the phone somehow, now that I am receiving it activated?
5) I understand I should use the firmware umbrella to save myself a 4.0 SHSH (while staying on 3.1.3) in case I want to unlock in that version later, when possible. Will doing spirit followed by Ultrasnow on 3.1.3 now harm my future options with the device?
6) If my unlock don't go smoothly and the phone gets in a state that its firmware needs to be restored, it can then only be a 4.0 phone thereafter and cannot be unlocked because 4.0 cannot be jailbreaked. So I take it I have only one chance to get this right, or I will not be able to unlock, right?
Thanks in advance for any advice.