Cydia App: Firmware 3.1.3 App – Change Firmware 3.1.2 To 3.1.3 On iPhone, iPod Touch
Firmware 3.1.3 App is an application that changes your firmware from 3.1.2 to 3.1.3, tricking applications in the App Store and iTunes. This prevents you from any hassles to upgrade to the newest FW (3.1.3) in iTunes and you can continue installing current App Store apps.
Note: ONLY supported on FW 3.1.2, since FW 3.1.3 are identical. Your iDevice requires to be restarted. This doesn’t update your firmware to 3.1.3, it’s tricking your iDevice by changing the file at /System/Library/CoreServices/SystemVersion.plist.
Screenshots and video demonstration below:
1) 3.1.3 is just 3.1.2 API with jailbreak closed. So any app written for 3.1.3 should run on 3.1.2. There is no point letting appstore prevent your install. Appstore developers that force 3.1.3 are idiots. You can solve this yourself now.
2) This prevents iTunes from nagging you to update your iPhone firmware or auto updating it. If you have a non-technical user using the device, this prevents accidental updates to 3.1.3 wiping out the jailbreak. You must reboot the iPhone after installing this in order to have iTunes recognize the version 3.1.3.
Firmware 3.1.3 App is available in Cydia, from BigBoss repo for FREE