Apple has stopped signing firmware older than iOS 6. This means that downgrading to an earlier version of iOS requires SHSH blobs and custom IPSW files.
Luckily for iPhone 4 and iPhone 3GS owners who have saved their SHSH blobs, there is a procedure that will downgrade your device to iOS 5.1.1. Full instructions on how to downgrade from iOS 6 can be found here.
Do you miss Google Maps? Did the iOS 6.0 update shorten battery life on your A4 device? Whether you upgraded by mistake, or you're just looking to bring back the older firmware, now you can downgrade your iPhone 4 or iPhone 3GS to iOS 5.1.1. The following iOS downgrade instructions work on most A4 devices, including the iPod touch 4G.
Now that Apple has stopped signing older firmware, you must have your SHSH blobs saved for iOS 5.1.1 for this procedure to work properly. Downgrading will also require that you have the appropriate IPSW firmware file downloaded to your computer. You can grab iOS 5.1.1 for the iPhone 4 here, or for the iPhone 3GS at this link. Make sure you know where this IPSW file is saved before starting the instructions below.
Good news for owners of the iPhone 4S and iPad 2 looking to downgrade from iOS 5.1. iH8sn0w announced the discovery of a loophole that makes it possible to downgrade any A5 device to iOS 5.0.1. Not only this, but the developer has successfully restored an iPad 2 to iOS 5.0.1 using the procedure.
Found a loophole in Apple's apticket system. Restored my iPad 2 to 5.0.1 from 5.1. Works on all A5 devices. :)
— iH8sn0w (@iH8sn0w) March 25, 2012
Downgrading an iPhone, from iOS 5 to 4.3.3 for example, requires saved SHSH blobs since Apple stops signing older firmware when an update is released. It's likely that the loophole iH8sn0w has found will also require saved SHSH blobs to work.
Are you missing some key jailbreak tweaks now that you've updated your iPhone 4 or 3GS to iOS 5 firmware? Already tired of dealing with all of the shortcomings in iOS 5 notification center? Luckily if you have saved your SHSH blobs you can easily downgrade and return your iPhone to a jailbroken state (and reinstall LockInfo!)
In order to downgrade you must have saved SHSH blobs. Pictured above are how saved SHSH files appear for each firmware version in Cydia, when they are saved to Saurik's server. Follow these steps to downgrade to earlier firmware, including iOS 4.3.3 for an untethered jailbreak with JailbreakMe.
So for whatever reason you went ahead and updated your iPhone to iOS 4.3.4 in iTunes. Normally this is no problem, except for the fact that your want to jailbreak your device untethered. Turns out an untethered iOS 4.3.4 jailbreak solution doesn't exist right now. Is there any way to return to iOS 4.3.3 and jailbreak?
According to the latest research by iPhone Dev-Team Apple has taken steps to make iOS 5 more difficult to jailbreak and downgrade. Although the limera1n exploit used for iOS 4.x jailbreaks still works in beta iOS 5, only a tethered jailbreak is possible at this time. Starting up a jailbroken iPhone tethered requires that the device be connected to a computer while booting.
It's not clear if Apple's move can be countered in the near future, as the company will begin to generate a unique APTicket every time the iPhone is restored. Not only this, but the APTicket will be verified every time the device is turned on.
Sometimes for whatever reason an iPhone firmware upgrade ends up being counterproductive or causes issues with your individual phone. Maybe you're experiencing battery life problems with iOS 4.1 on your iPhone 3GS. Updates can even happen by accident with the wrong click of a button, wiping a jailbroken device.
If you have already saved your SHSH files for one or more earlier firmware versions on Saurik's server, you can follow these steps to downgrade from iOS 4.1.
First of all, downgrading your iPhone firmware is only possible if you have saved your SHSH files. For those who took this precautionary step, use these instructions to downgrade.
Note that downgrading your iPhone firmware is only possible if you have saved your SHSH files. For those who prepared by taking this step before upgrading, see the following instructions to downgrade.
First download your SHSH files to your computer with TinyUmbrella.
1. Install TinyUmbrella.
2. Plug in your iPhone and run TinyUmbrella.
3. In TinyUmbrella select Advanced Options and choose 4.0.1 firmware.
As we reported earlier, many iPhone users have encountered problems with the iTunes 9 and iPhone 3.1 firmware upgrade. Until Apple comes out with fixes for these bugs, the solution may be a downgrade to earlier software versions.