I can't answer either your version question or your "refreshed design" question. I don't own that model camera. From experience when firmware is upgraded it is usually for security purposes or to improve functionality, as in IVS or SMD.
If the original vendor can't help, you're stuck looking around then guessing to find the most current. Have you checked the Dahua site? They usually have firmware listed, but it can be rather confusing to find firmware for a specific camera.
All this comes down to why are you trying to upgrade the firmware? If the camera works you'll be taking a major risk if you guess wrong when trying to upgrade. If it ain't broke, don't fix it.