Compatible iDevices
iPhone
iPhone X
iPhone 8/ 8 Plus
iPhone 7/7 Plus
iPhone 6s/6s Plus
iPhone SE
iPad
iPad 12.9-inch iPad pro 2nd generation
iPad 12.9-inch iPad pro 1st generation
10.5-inch iPad pro
9.7-inch iPad Pro
iPad 6th generation
iPad 5th generation
iPad Air 2
iPod
iPod touch 6th generation
Pre-Requisites:
1. Download the SHSH2 (of the iOS version you want to downgrade) you saved before on 3uTools or another tool.
2. Download NonceReboot12XX ipa file.
3. Download the iOS firmware you want to downgrade on
3uTools | iOS jailbreak & flash tool Here is the tutorial from 3u website. 
