installing W11 on W10 results in the entire drive being wiped. A new registry is created which contains nothing from the W10 registry. if it's within 10 days of upgrading to w11 there is a procedure to revert to w10.
if you want to go back see this
https://support.microsoft.com/en-us/windows/go-back-to-the-previous-version-of-windows-4fdf8a9e-ddc9...
