Botched Beta 4 update on iMac18,3. APFS disk seems to revert to a snapshot on restart.

System: iMac18,3. Baseline model with 1 TB Fusion Drive, formatted to APFS, and RAM upgraded to 24 GB.


I began the update process several hours ago, thinking it would be a smooth routine as usual.


When the App Store finished downloading Beta 4, I chose not to restart immediately. After a while, I hit Update again and let it restart my Mac.


It went through the usual processes, and eventually restarted to the login screen. I used the iMac a little, and then I chose to shut it down.


After I click on Shut Down, it was stuck on a black screen with the gray spinner at the bottom center. I waited about 10-15 minutes, and then forcefully powered off the iMac by holding down on the power button.


A few hours later I powered the iMac on, logged into my non-admin user, and everything was acting weirdly:


Apps would bounce in the dock and just stay there, without launching and misisng the active app indicator dot underneath them.


Everything was slow. Firefox wouldn't load websites even though the internet connection was working. The App Store offered me to update the Command Line Tools for Xcode 9 Beta 4, but when it finished downloading, the update failed with the message that the servers could not be contacted.


I restarted, and logged back into the same user. Even fewer things worked this time: no Finder, no Menu Bar. Continuous beach ball.


I restarted and logged into an administrator account. It was more usable. The App Store was again offering the Beta 4 update, but I only chose to update the Command Line Tools. The Beta 4 update disappeared but the Command Line Tools update was stuck on "Installing, Calculating..."


I restarted into Recovery Mode and ran Disk Utility checkup on the APFS boot drive. It finished successfully.


When I restarted back into the adminstrator account, I was unable to use the Terminal; it just stays stuck on a black screen, running the "login" process.


In /Library/LaunchDaemons/ I saw (and still see) com.apple.installer.cleanupinstaller.plist and com.apple.installer.osmessagetracing.plist


I tried moving them out to another folder.


When I restart now, all the changes I made to the Dock and other settings, including the creation of new users, as well as changes to files and folders, are reverted.


Everything, including the file system, gets undoed on restart.


What should I do at this point? Currently downloading each of the standalone Beta 4 links, from this post: https://forums.developer.apple.com/thread/83154?q=10.13