How to downgrade iOS 10
If you installed it on your iOS device 10 and received a “brick” or just not happy with the speed and stability of the operating system may perform a “rollback” checked 9.3.5 on iOS, until Apple stopped signing. To do this is not difficult, below I will tell you how.
Let’s start with the most important: if you do not want to lose your data after “rollback”, you should have a backup of iOS 9.3.5 — in iCloud or in iTunes on your computer. If you forgot to backup before installing iOS 10 and don’t want to lose data, you better not read further.
So, we will need a computer with the latest version of iTunes, iPhone, iPad, or iPod Touch with iOS 10 and iOS installation file 9.3.5, download for your device here. Then connect the gadget to the computer, open iTunes, then while pressing the Option (Mac) or Shift (Windows) click on the button “Restore”.
In the window that appears, select the installation file that you downloaded in the previous step, accept all agreements and carry out the installation. As soon as the “rollback” is done, iTunes will prompt you to restore from backup or configure as a new one. You can recover using backup from iCloud and backup to iTunes on your computer.
iOS 10 impressive speed and battery life, so these instructions will probably use only those who are experiencing serious problems after the upgrade. Moreover, even on older devices the new OS behaves consistently.