How would I know if an OTA update had happened/completed
You will see the OTA symbol
If the screen says “CPI” then it is not OEM. If you are using a SuretyCAM activated cell module, the panel should have been reprovisioned, (but apparently hasn’t)
The OTA update will not occur, until panel reprovisions. Then it will shown as 2GIG OEM
You can also try flashing 1.9.6 to the Q optimized (see link above) main panel, then going to 1.13. As long as the firmware screen shows a branded firmware version though, (e.g., “CPI”, or “Vivint”), you will not be able to remove the branded logo by overwriting the firmware twice. It is possible that later firmware releases are preventing the overwrite (so try 1.9.6).
The only other way that I know of to reprovision a branded panel to OEM 2GIG is with a cellular module/service plan.
Power down, replace the CPI cell module with the Surety one, power back up, successfully perform the cell phone test and wait. Panel will do a OTA update, reprovision itself, and you should see the surety logo.