UPDATE : There seems to be a bug in ultrasn0w 1.2.8 when used with iPhone 4 having modem 01.59.00 on iOS 6.1. So Pls. do not proceed with following steps until this gets fixed.

Users relying on Ultrasn0w software carrier unlock can now upgrade to Apple iOS 6.1 as it can now be jailbroken using evasi0n and is now supported by ultrasn0w 1.2.8 update, do keep in mind that you must have the baseband (modem) preserved to one supported by ultrasn0w. Follow the guide posted next to upgrade, jailbreak and unlock iOS 6.1 while preserving the baseband.

Users relying on software carrier unlock ultrasn0w must use sn0wbreeze created custom IPSW firmware to upgrade there iDevice to an upgraded iOS version without updating the baseband which breaks the unlock. However, Apple iTunes prevents users from upgrading or restoring to these custom IPSW files and errors out the process with codes 3194 and 1600 - for which we have shared solution earlier. Here is an step-by-step guide to restore an custom IPSW file to iPhone using iTunes the correct way without any errors.

The cat-and-mouse game between jailbreakers and Apple is getting tough for hackers with every new release of Apple iOS, as it plugs existing loopholes which they exploit. Anyone trying to restore Apple iOS 5.1.1 on iPhone 4 and 4S will face iTunes errors like 3194 and 1600 while trying to flash an sn0wbreeze customized IPSW file, even when having saved SHSH blobs and using TinyUmbrella TSS server. The solution to this problem is to have the custom .IPSW firmware file stitched with previously saved SHSH digital signatures, follow the detailed instructions ahead to get this done using sn0wbreeze.

Few days ago Apple started detecting jail-broken devices via iBooks denying access to books if found positive, to counter this sn0wbreeze v2.2R3 is now available for download patching the gap Apple used to detect sn0wbreeze jailbroken phones.