Hello Adarsh P S,
welcome back to the Polycom Community.
The REST API could be used to factory restore the phones but this is not yet public. I assume your Polycom contact who provided you with the Dev Signed Firmware for the Demo Trio could help you with this.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Best Regards
Steffen Baier
Polycom Global Services