Updating a Full iPad via iTunes Recovery Mode
How to force an iOS update on an iPad with insufficient storage by using Windows iTunes and Recovery Mode.
Phase 1: Windows Prep
Install the latest version of iTunes on your Windows PC and connect your iPad using a high-quality USB cable.
Phase 2: Entering Recovery Mode
For iPads with a Home Button: Press and hold both the Home and the Top (Power) buttons simultaneously. Keep holding them even when you see the Apple logo.
For iPads without a Home Button: Press and quickly release Volume Up. Press and quickly release Volume Down. Press and hold the Top button.
Phase 3: Update vs Restore
When iTunes detects the device, a pop-up will appear. Select 'UPDATE'.
Wait for iTunes to download the firmware. If the download takes longer than 15 minutes, the iPad may exit Recovery Mode.
Phase 4: Completion
Once the progress bar on the iPad finishes, the device will reboot. Follow the on-screen prompts to complete the setup.