: Open iTunes, hold the Shift key (Windows) or Option key (Mac), and select your custom IPSW to restore without errors. Safety and Compatibility
: Attach your legacy iOS device to your computer via USB.
Review and Tutorial on how to get and use iREB and f0recast.
: Versions like RC2 were specifically optimized for iOS 4.0.x and 4.1, which were the primary firmware versions for the iPhone 3GS and iPhone 4 era.