1. use CUSTOM ipsw files in order to preserve their baseband and then jailbreak iOS 5.1.1 using Custom ipsw after that you can follow the below steps to untether there iDevice and to unlock you just need to download Ultrasn0w from cydia install and unlock your iDevice.

Compatible devices: iPhone 4 iPhone 3GS iPod Touch 3G iPod Touch 4 iPad a

Apple iOS Custom 5.1.1 (Iphone/Ipad/Ipod) Apple iOS Custom 5.1.1 (Iphone/Ipad/Ipod) | 4.91 GB

Compatible devices: iPhone 4 iPhone 3GS iPod Touch 3G iPod Touch 4 iPad a
Language: all available, as in the original firmware.

Apple officially released iOS 6.1 Beta 3 for developers

There are currently no new information will be updated

What you are using iOS 6.1 Beta 2 can fully direct dowload iOS 6.1 Beta in the form of OTA in the home machine

For the last few months, Apple has been intensively testing iOS 6.1, the next minor update for iOS 6. Up until now, only developers willing to spend $99 per year on an Apple developer subscription had access to beta copies of this release, but now that the final version is upon us, everyone can take advantage of it. Here is how to download it right now.

Xilisoft iPhone Magic Platinum v5.4.9 build 20130222
| 49 MB

Taking Your iPhone 4S to the Max: For iPhone 4S and Other iOS 5-Enabled iPhones
Publisher: A p r e s s | 2011 | PDF | ISBN: 1430235810 | 524 pages | 19.9 Mb