I do own the Air II HG9M and I upgraded from 1.80 to 2.02.
I did the upgrade via Windows, and it worked flawlessly. I’ve even updated to Win 10 lately. Updating the BIOS didn’t have any adverse effect on the tablet (no partition loss of whatsoever) but I did a backup of the data, extract the win 8.1 product key, and prepared the Teclast “restore set” just in case.