OdysseusOTA 2 let you downgrade iPhone 5, iPhone 5c, iPhone 4s, iPad 3 and iPad 2 to iOS 8.4.1
This new downgrade method lets you downgrade A5 devices to lower version like ios 8.4.1 the developer resease a video tutorial showing how to downgrade an iPhone 5 (iPad2, iPad3, iPhone4s) from any version to iOS 8.4.1. It means if you are one ios 9.0.x or 9.1 you might be abel to downgrade your idevice with this steps.
This works because apple still signs 8.4.1 OTA blobs for these devices and we have keys for them. This method does not work on any other iOS version.
PLEASE NOTE : jailbreak is required for downgrading.
this also works on linux operation system.
@tihmstar, the developer of OdysseusOTA 2 explain how it works:
All commands are also listed in the README.txt inside the zip, you can simply copy and paste
Currently supported devices: iPhone5,2 / iPhone5,1
odysseusOTA2-v1.0.2.zip SHA1: 0c8a5c6f02c883c371256275fec45c9e22a5f8ea
(added iPhone5,1 bundle)
odysseusOTA2-v1.0.zip SHA1: d15df971ec533bc91a31e392aff5e2b0c5c78733