It wont be long before some newer apps from the iTunes App Store will require you to have the latest iPhone 3.1.3 firmware in order to install a particular app. Earlier this month, Apple released the new iPhone OS 3.1.3 for iPhone and iPod touch which upgraded the baseband to 05.12.01 for iPhone 3G and iPhone 3GS, hence making it impossible to unlock them on the latest firmware with the newer baseband.
If for some reason you have decided to hold off from upgrading to this minor update until the new iPhone OS 3.2 or iPhone 4.0 is available, you can fake your firmware to iPhone 3.1.3 which will make iTunes believe you have the latest firmware installed, hence allowing you to download and install all the apps from the App Store.
Simply follow the steps below to fake your firmware to iPhone 3.1.3. This wont in any way effect your baseband/unlock or anything in real. All it does is change the version number from iPhone 3.1.2 to iPhone 3.1.3.
Step 1: You will need to have a jailbroken iPhone or iPod touch on iPhone 3.1.2 in order to get this to work. Follow our complete step by step guide posted here to jailbreak your iPhone with iPhone 3.1.2 firmware.
Step 2: “Fake 3.1.3” app is available in Cydia on http://cy.sosiphone.com/ repository. Make sure you have added http://cy.sosiphone.com/ repo in Cydia.
Step 3: Now simply search for “Fake 3.1.3” in Cydia and install it. You must restart your iPhone for the changes to take effect.
Step 4: After reboot, navigate to Settings –> General –> About. You should now have “3.1.3 (7E18)” listed beside “Version”.
You can also follow our complete jailbreaking guide for iPhone 3.1.3 firmware for iPhone 2G, 3G, 3GS and iPod touch 1G/2G using redsn0w 0.9.3, redsn0w 0.9.4, sn0wbreeze, PwnageTool 3.1.5. Unlocking can be done using ultrasn0w or blacksn0w.
For iPhone 3.1.2 firmware, you can use blackra1n, PwnageTool, redsn0w, sn0wbreeze, ultrasn0w and blacksn0w to jailbreak and unlock your iPhone and iPod touch.