Do these links only work for iphones. if so how do you downgrade ipod touch from 4.2.1 to 4.1? Ami says: 2010/12/09 at 3:01 am. How To Downgrade IOS 4.2.1. Feb 7, 2010 If at any point in time you updated your iPhone to firmware 3.1.3, then you iPhone 2G; iPhone 3G; iPhone 3GS (old bootrom); iPod Touch. Download iOS Firmware 3.1.3 (7E18) for iPhone 2G. File Name iPhone1,1_3.1.3 _7E18_Restore.ipsw; File Size 227.28 MB; Device iPhone 2G; Downloaded.