Can you go back to the original to the frimware and if so how?
You can revert back to the 1st firmware update that has been posted, but the original firmware that comes on the Fuzes from the factory is not posted anywhere. There have been several updates, each one that corrects or fixes an issue and/or includes new enhancments as they are developed. So yes it’s possible; just use the Search function here to ferret them out.
It would go quicker if you knew the firmware version number, but otherwise in your Search results just look for the Subject header ‘Fuze Firmware Update’, then read the release notes to determine which one you want to install. Manual installation instructions are written within the post.
Having said that, I’m sure you have your reasons for wanting to ‘back-date’ the firmware, but given the improvements the newer versions offer anyone here will ask “Why?”