To move from Windows 11 to Windows 10 there is a default and modified go back period after an upgrade.
These are 10 and 60 days respectively.
If a clean install of Windows 11 had been performed then there is no go back option.
If there were backup images made there there is an unlimited go back period by restoring an image.
One method to move from Windows 11 to Windows 10 is a clean install:
- Manually back up important files
- Find a flash drive that you can format ( > or = 8 GB)
- On a working Windows computer create a bootable Windows 10 Media Creation Tool (MCT) (Windows 10 iso)
https://www.tenforums.com/tutorials/2376-create-bootable-usb-flash-drive-install-windows-10-a.html
https://www.tenforums.com/tutorials/9230-download-windows-10-iso-file.html
https://www.microsoft.com/en-us/software-download/windows10
- Move the bootable flash drive to the applicable port on the problematic computer
- Boot to the flash drive
http://www.disk-image.com/faq-bootmenu.htm
- Delete all partitions making an unallocated drive
- Clean install Windows 10
https://www.tenforums.com/tutorials/1950-clean-install-windows-10-a.html
- Reinstall drivers displayed on the computer, motherboard, or component manufacturer websites
- Reinstall applications
- Restore backed up files
- Make free backup images
(Acronis, Aoemi, EaseUS, Macrium, Paragon, etc.)
https://www.tenforums.com/tutorials/61026-backup-restore-macrium-reflect.html