Just had this problem yesterday with a friends desktop PC, infinite boot-loop (could not restore to previous version) after a Windows 10 update. Removed the HDD, installed in an external dock (can use an enclosure), then connected to another PC to access and backup files.
Options 2&3 suggested by midnightfrolic might work too but there's no guarantee they won't screw something up as well... I have little faith in MSFT's abilities these days to automate successfully so would strongly recommend option
#1 if your files have any signifiant importance to you.
If you feel uncomfortable doing it yourself or don't have the resources, find a friend that'll offer their assistance.