Installing or Updating iOS Using iTunes
You can’t directly downgrade from iOS 11 Beta 2 to iOS 10.3.2. That’s why you should downgrade in two steps. You can either downgrade to iOS 11 Public beta 1 or iOS 10.3.3 Beta first. Later use restore image of 10.3.2 or simply update using iTunes.
Step 1 : Connect your iOS device to iTunes
Connect your device to iTunes using a USB cable and open iTunes.
Step 2 : Download the iOS Restore Image
If you are currently running iOS 10.3.3 beta: For devices that currently have 10.3.3 beta installed and have not previously had iOS 11 installed, skip this step. You can simply update using iTunes by booting into Recovery.
If you are currently running iOS 11 beta: For devices that currently have iOS 11 beta installed, you must restore 10.3.3 beta first. Download the iOS 10.3.3 beta software restore image for your device from the download page.
Step 3 : Put your iOS device into Recovery Mode to install iOS 11 beta.
On an iPhone 7 or iPhone 7 Plus:
On an iPhone 6s and earlier, iPad, or iPod touch:
Restore your iOS device.
iTunes presents you with options to restore or update your iOS device. If you are running iOS 10.3.3 beta, choose “Restore” or click “Update” to get latest stable release. If you are running iOS 11, hold the Option key in Mac (Shift Key in Windows) while clicking “Restore,” then select the Restore Image that you downloaded. You’ll need to confirm that you want to set it back to its factory settings by choosing “Restore” and then iTunes will erase your device.
For going back to 10.3.2 from iOS 11 Beta, you’ve to restore downloaded 10.3.3 beta image. Later setup device then reboot into recovery and update you iOS device using iTunes. iTunes will download latest stable release i.e 10.3.2 and install it in your iPhone.
Activate your iOS device.
Once completed, sign in with your Apple ID from iTunes to activate your device.
Restore from your iOS backup in iTunes to get messages, files and settings.
When iTunes prompts you to restore all of your information from a previous backup, choose the iOS backup that you created in iTunes before you installed the iOS public beta. Then select “Continue” and iTunes restore your device.
Restart your iOS device.
After your device has restored, it will shut down. Restart the iOS device and follow the onscreen instructions from Setup Assistant.