DA Version?

What is the DA version in cnMaestro for a PMP450 AP referring to?

Does this value change when software is upgraded or downgraded?

I've never heard of this... where are you seeing this? Do you have a screenshot or document where this is mentioned?

It is version number cambium internally uses to track what version of device agent software is running in the radio,

version may or may not change across the releases.