Stephen:
Unfortunately, the OID you want doesn't currently exist, and I don't have an SNMP workaround for you at this moment.
I'd suggest you open a Feature Request, which you can do online at the Support Portal.
Jairo:
The screenshot you provide is absolutely correct and expected behavior.
That partition has been written with the 16.1.3.6 image; it cannot be uninstalled, only installed over.
If you wish to return to the 15.x image present on the primary p...