How to roll out of iOS 9.3
Honestly, we don’t know for what reasons you may need to “rollback” to iOS 9.3 to an earlier version of the mobile operating system from Apple. But suddenly with the update you found any incorrect operation of the device, bugs or freezes — then install iOS 9.2.1, it makes sense. And to make it easier than you think.
To begin, make a backup of the device. It is better and in iTunes and in iCloud — so you will protect yourself from losing important information. After that, download the firmware file iOS 9.2.1 for your iPhone, iPad or iPod Touch. You can download it for example here.
Start iTunes, and then connect to the computer. Select it in the list and click “Restore iPhone” while holding Alt/Option or Shift (on Windows).
Select the downloaded firmware file and start the recovery. Once the process is complete, iOS will ask you to set up your device as new or restore from backup.
But if you want to enjoy the cool functions like Night Shift and setting the password on the notes to ‘fall back’ we would not advise.