How to downgrade from iOS 9.3.5 back to iOS 8.4.1 UNTETHERED without saved SHSH Blobs on any 32-Bit device? Simple! In today's tutorial I am going to show you how to do so step by step.
Before we get into it, you should know that this procedure is possible without SHSH blobs because Apple signs iOS 8.4.1 OTA. What this means? Well, you can't downgrade to iOS 8.4.1 normally via iTunes, but if you are jailbroken (for example on iOS 9.3.5 with Phoenix Jailbreak) you are able to fake the iOS version so that your phone will think it runs iOS 6.0. In this case, Apple doesn't allow your device to directly go to iOS 9.3.5, you will receive the update for iOS 8.4.1 first so that you can update from 8.4.1 to 9.3.5, which, of course, you will not do.
This procedure, although not hard, is a bit dangerous if done wrong, so please pay attention to what you modify, double-check what you change and keep in mind I am no way liable for damages to your device or jailbreak, you're doing this at your own risk. I will try to provide support if you get errors, but don't bet on that.
Keep in mind that aside of the incomplete yalu jailbreak by Luca Todesco, there is currently no Jailbreak for iOS 8.4.1! I am not very sure how incomplete yalu is or whether it works to jailbreak but it is unstable, so I can't tell you exactly about it, but for the moment, assume you're downgrading for speed improvement on these old 32-Bit devices like iPhone 4S and iPod Touch 5 and so on, not for jailbreak.