There are multiple firmware revisions on the same Pro cams because of the chip shortage. My 4 2 Pros are on 4.6.6. My 2C pros are on older revs, one as old as 3.8.4. Don’t get hung up on the revision number because it can be different for the same model. Lots of people blame firmware for other problems.
Also, Eufy only updates on their own schedule to prevent having to rollback problems to everyone with a particular model. So, even if you do a manual update, you won’t get a newer revision. Trust me, this is better than letting everyone manually update their devices whenever someone on Reddit says they got a newer rev. Essentially, there is no manual update.
As far as night vision goes, if you turned on Night vision in the app menu for each camera, you have done everything you can do. Do you hear a click when the filter is actuated when you move the camera from a lighted room to dark? That means the camera going in or out of night mode. If you don’t hear it, did you remove the plastic protection layer from the lense? That got me one time when I was in a hurry.