If you have not done this yet, try leaving the tablet running overnight (with the power connected), to determine whether or not the condition that you describe is indeed due to a backlog of updates. The anniversary update alone will take quite a long while.
Please advise this forum of your results and findings.
I have tried that twice with no success. I have left it again, this time power not connected, to see if anything changes. Otherwise, I guess my options are to either install windows 8.1 via USB stick (not sure if it will be recognized if the tablet does not boot into windows) or just wipe it and turn it into android only tablet. Will let you know.
Still not booting into windows after leaving it for 20 hours. I have made the USB drive with windows 8.1 to reinstall it. I can enter the BIOS but cannot see any option to boot from USBĀ under the “Save and Exit” menu and scrolling down to the “Boot Override” option. I I changed the default from the OS option to something ‘windows’. Now I see the boot screen again with the wheel turning but with something in Chinese underneath. The USB drive is clearly recognized as the red light on it is on. I am going to leave it like this and hope that it will eventually boot via the USB and I can reinstall windows.