Downgrade from iOS4 to 3.1.2 to Jailbreak 3GS(Mac)

[attanasi0]

I know I am not the only one who updated to iOS4, be it GM or Official, once it came out without thinking of how they were going to jailbreaking it. This is a way to go back to 3.1.2 (tested on GM, cannot confirm for official) so you can jailbreak using blackra1n and then update back to jailbroken iOS4.
Is worked 100% on my old bootrom 3GS.

Step 1
Go to /etc/hosts and add this entry "74.208.10.249 gs.apple.com" at the end of the document. You might need to change permissions to be able to do it.

Step 2
Go to www.felixbruns.de/iPod/firmware/ and download the IPSW for 3.1.2 for your 3GS device.

Step 3
Put your device in DFU mode and restore using the Alt+Click option you should already know about, pointing it to the 3.1.2 firmware.
Once the restore is done, you will get an error 1015, don't worry about it.

Step 4
Your device is now in recovery mode, DO NOT PUT IT BACK IN DFU, and restore again to 3.1.2 using Alt+Click, doing a normal restore.
You will still get the same error 1015.

Step 5
make it ra1n

Step 6
Update to iOS4 Custom using Pwnage Tool 4.0.1 using other tutorials


I did not come up with this thing, just made it simpler for people to use. This is the same method that was used to go back from 3.1.3 to 3.1.2

If anyone can confirm that it works for iOS4 Official, that would be great.

 

[Neolithium]

It will work fine for those with 3.1.2 SHSH's backed up, but for those without, they will be SOL.

 

[Imsuperjp]

this only works if you saved you shsh blob on cydia

 

[attanasi0]

I don't think I had them saved, I was on 3.1.2 jailbroken via blackra1n, but then I updated some app and my iPhone bricked, I restored it using iTunes and updated to 3.1.3 not jailbroken at all, then updated to iOS4-GM, not jailbroken, and only then I went back to 3.1.2
Were they still saved or is it magic ?

 

[Neolithium]

It's not magic. If it could be done without them being saved, everyone with 3GS's would be doing it and not waiting on a new JB tool

 

[attanasi0]

It's not magic. If it could be done without them being saved, everyone with 3GS's would be doing it and not waiting on a new JB tool

Oh well, I thought I would help. Does Cydia automatically saves them then ? And they stay even if you are not jailbroken anymore ? Meaning anyone who jailbroke their iPhone once would be able to go back to some old firmware and work their way up ?

 

[Imsuperjp]

there is something in cydia that you can click on t hat would save it for you. Make my life easier or something like that

 

[gooddeal]

attanasi0, can you either link to a detail instruction or edit your post so that newbe can follow your instruction. I used to keep up with this thing 2 years ago.

I just got a 3GS, the guy updated to official 4 but he said that it was jailbrook before that. thanks.

 

[AHDuke99]

If I downgraded to 3.1.2, jailbroke it with PwnageTool, unlocked it and wanted to then upgrade to 4.0, is that possible? And keep my unlock?