If a set of dentures cleaned in a sonic jewelry machine becomes damaged, does that void the warranty?

No. Ultrasonic machine is a great way to clean dentures. That is what dentists often use.
No. No and talk to your dentist about the parameters of the warranty.
Should not. In. Dental offices dentures are cleaned in ultra sonic cleaners.
Depends. You would have to speak to your dentist or the lab who made the dentures. Dental offices use ultrasonic cleaning machines to clean dentures also. However, there are specific solutions that are used to remove stains and tartar from the denture. Also, it is usually placed in a beaker or container to prevent it from direct contact with the bottom of the us tank.