The Sophos XGS families the tool has been measured on; others are marked "coming soon" and added as they are tested.
Yes — your own licensed firmware image, which you drop onto the USB. We never distribute it.
One licence can perform the repair on that appliance up to three times, in case a first attempt needs a retry.
No. It is kept only as a one-way fingerprint, so a repair can be authorised without the serial itself being held.
No. It is an independent open-source project and distributes no Sophos software or firmware.
Yes — the appliance shows a short code you paste on this site, and you type the signed reply back.