I really don't know what happened or how I got my desktop back. I only know the "built-in" ways of doing things.
Regarding the missing box, the Great God Google displays that MANY people with the same problem - just look There also many "solutions". I think I can try that FOLLOWING is one that I found:
PS: If you don’t want to modify Registry Editor manually or if you can’t see above mentioned key in Registry, you can run following command in Command Prompt directly:
reg ADD "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\PasswordLess\Device" /v DevicePasswordLessBuildVersion /t REG_DWORD /d 0 /f
It’ll do the same job and bring back missing checkbox in Windows 10.
Big thanks toWinaerofor finding the issue…