New
#20
Never mind..Builds are not version boundaries. There are dozens of builds in the same version. What triggered the concern was the change from Windows version 10 to Windows version 1511. 1511 is not a build. It is a version of Windows in the same way a new service pack changed Windows 7 to Windows 7 Sp1. Different versions. You can go back to 10240 from build 10576 without losing apps but you can't go back to 10240 from 10586 without losing apps because you have crossed a version boundary. The software won't let you. You are free to do it but your options have changed.
As far as the windows.old file is concerned, of course it would be 10240. But that is the problem. Prior to doing the November Update, the windows.old file wasn't for 10240 for users recently taking advantage of the Get Windows 10 offer. The windows.old file was for the legacy OS. And that is exactly the issue here. You have hit the nail on the head. The recent Windows 10 adopter has lost his chance to revert to the legacy OS. Of course he can use a system backup...if he made one.