iOS 6.1.2 is compatible with the following devices.
iPhone 3GS, iPhone 4, iPhone 4S, iPhone 5
iPod Touch 4th generation, iPod Touch 5th generation
iPad 2, iPad 3, iPad 4, iPad Mini.
You can upgrade to iOS 6.1.2 using Over The Air (OTA) updates or by connecting to itunes on your computer.
To update your iPhone, iPod or iPad using OTA updates, go to Settings > General > Software Updates and click Install update. If you plan to jailbreak your device after upgrade, you should not use OTA updates but use the second method as below.
You can download iOS 6.1.2 IPSW foe your device and connect to iTunes on your computer and use the downloaded IPSW to restore. To do so, download iOS 6.1.2 IPSW, Connect your device to comouter, open iunes, and take backup of your device. After that, press and hold Shift key (on Windows) or options key (on Mac) and click Restore button in iTunes. Release Shift/Options key and browse to the IPSW file you downloaded and select it. The restore process will start now.
If you rely on carrier unlock like uptrasn0w or SIM interposer like Gevey SIM or R-SIM, you must preserve your iPhone's baseband to retain unlock. In this case, create a custom IPSW using sn0wbreeze or redsn0w on Windows or PwnageTool on Mac and restore using that.
As usual, you can download iOS 6.1.2 IPSW for your iPhone, iPad or iPod touch from Blog O'Nerd Downloads. Click here to download iOS 6.1.2 IPSW from Blog O'Nerd Downloads using Direct Download Links.
iOS 6.1.2 is jailbreakable using evasi0n jailbreak tool available for Windows, Mac and Linux. You can download it from www.evasi0n.com
