I’m sorry to hear that you lost your photos after upgrading to Windows 11. The Windows.old folder is created when you upgrade from one version of Windows to another, and it contains files and settings from your previous installation. However, this folder is automatically deleted after 10 days or after running Disk Cleanup, so it’s possible that your photos were deleted along with the folder.
If you have a backup of your files, you can try restoring your photos from the backup. If you don’t have a backup, you can try using a file recovery tool to see if you can recover the deleted photos. Keep in mind that the chances of successful recovery decrease the longer you wait and the more you use your computer, as the deleted files may be overwritten.
As for upgrading back to Windows 11, you should be able to do so without any problems as long as your computer meets the system requirements for Windows 11. However, keep in mind that upgrading to a new version of Windows can sometimes cause issues with drivers and software compatibility, so make sure to backup your important files before upgrading.