help with 3gs 3.1.2 old bootrom re-jailbreak/unlock

[periohead]

hello, i bought a used 3GS 16GB iOS 3.1.2 with baseband 05.11.07 old bootrom previously jailbroken with blackra1n and unlocked (backsn0w). Cydia icon appears but there's no other application installed and all the contacts and messages were also removed from iphone (i don't know if the user erased all contents and settings). so problem is that cydia crashes everytime i try to open it and it will not install using blackra1n on the iphone. when i use iphone browser the iphone is not recognized as jailbroken and no ssh is installed on the iphone so i'm not being able to get to the file system and i don't have any SHSH firmware backup. For now my sim works properly but i have some issues with the iphone (youtube, cydia and push notifications not working....)
so is there any way to rejailbreak the iphone without loosing the unlock and how? can i use redsn0w 0.9.2 and then ultrasn0w to unlock after the blackra1n or i have to restore my iphone to factory settings using itunes before? will i preserve my current baseband? thank you

 

[PsstGreek]

Since all your options are pretty much out the only solution would be to upgrade to 4.2.1 since you don't have the SHSH saved. But to make sure that you do or don't, hook up the iPhone to TinyUmbrella see.

If you know anyone with a Mac you can use the newest version of PwnageTool and create a custom 4.2.1 ipsw, saving your baseband to upgrade and unlock.

 

[Myzhi]

Since you have the old bootrom, you can have a untethered 4.2.1 JB. Instructions: Create or find a 4.2.1 custom firmware file (one that keeps your current baseband), use Redsnow or Pwnagetool to put phone into a special DFU mode, and then, restore with the custom firmware file through iTunes.

 

[periohead]

ok thank you! well i tried tinyumbrella there's no shsh saved for my device, i saved the shsh for the 4.2.1 anyways. so now i have to upgrade to 4.1 or 4.2.1 using pwnagetool... but if any problem occurred can i still restore iphone to original factory settings using itunes and then jailbreak-it again ?

 

[Myzhi]

ok thank you! well i tried tinyumbrella there's no shsh saved for my device, i saved the shsh for the 4.2.1 anyways. so now i have to upgrade to 4.1 or 4.2.1 using pwnagetool... but if any problem occurred can i still restore iphone to original factory settings using itunes and then jailbreak-it again ?

Without saved old SHSH files, you can only install 4.2.1 firmware. And, if you do it without a custom firmware (one that keeps your current baseband = 5.11), it will also update your baseband to 5.15 which means no more unlock. Since you have the old bootrom 3GS, you can have untethered JB on 4.2.1. The issue is keeping your baseband for the unlock.