ReactOS, the open source recreation of Windows NT
Why? If you haven't moved passed NT by now, its about time to just wipe the slate clean and start all over because the time and money you're going to spend trying to upgrade everything to the latest and greatest is going to be absurd.
All modern Windows systems are built on top of Windows NT. Windows 10 is on NT version 10.
Yep. Kernel changes very little. All the other stuff that you actually interact with changes lots.