Windows 10 update 1803 loses Startup on Dell Inspiron Laptop

At the end of the update process during restart Windows 10 is dark desktop where all shortcut icons are not working with an “object is unavailable” error message.
At this point none of the shortcuts or Windows icons are functional. Startup does nothing, the taskbar is locked and can’t be unlocked. I can do Alt-Ctrl-Del for the Switch user menu and from there start task manager but there are no processes running in task manager.

Actions taken:
Bootup on system repair disk and run System Repairs, System Restore, Return to known good system but the result for all is “Windows ran into a problem and can’t fix your PC” message.
Selected command prompt and ran chkdsk /r .... no problems found.
Selected command prompt and ran sfc /scannow .... no corrupt of missing files found.
Decided to post this problem before I try the System Image Restore option which will remove all my data files and applications on the system drive. Are there any other suggestions as to how to restore the Windows 10 system?

Thanks Ken, those are useful suggestions. The Problem has been resolved. Using the Shift key and restart, I was able to get to the advanced boot page and select Reset System and save data files and the reset went successfully(it was slow). During this process the 1803 update was completed. The one remaining issue was I lost all my network settings and had to start over in making a network connection and getting the WiFi enabled. So far, everything seems to be working OK(why did MS remove home group?)