With the earlier builds, I had UAC disabled in the registry( just as I do for my host machine Windows 8.0 Pro) and everything worked fine. It was in your sister forum eightforums tutorial that I learned how to disable UAC in Windows 8.
I also use Start8 and Windowblinds on both OSes. I have zero interest in Metro apps and that hideous Metro side with garish tiles. I am on a desktop and have no need for Metro apps. I had believed MS when they said Windows 10 would address the complaints with Windows 8 on desktops so that is why I decided to do the Win 10 Pro Technical Review on Hyper V virtual machine. IMO, NONE of the complaints have been addressed though.
Since I have zero interest in Metro side or using Metro apps on desktop side (I have plenty of programs and don't need any more), I am perfectly happy with Metro apps disabled due to my having disabled UAC in the registry. (I would uninstall all the Metro apps but that can't be done as I learned on Windows 8 Pro - they can be hidden but not uninstalled taking up precious space on my SSD while never used).
On the previous builds, even with UAC disabled I could access Metro side, if absolutely needed, via the Start8 Menu (just as I can on Windows 8 Pro). I can't do that in this build and the problem is not with Start8 (which has a new version for this build) but I think is because I have UAC disabled. So, I have use of desktop with this build but I cannot access Windows Updates as that is now accessible ONLY from Metro side. With UAC disabled, I am not bothered by Cortana, search in taskbar (I don't use Windows search...I use Agent Ransack which is far superior), etc. which is a relief.
So, my question is how do I keep UAC disabled yet be able to access WU if needed (or send feedback to MS since that too now is on Metro side)?