A dashcam can change focus as in the focus will slide due to heat most often, if the focus shift is permanent you can indeed focus the lens again.
To do that you need to take the camera apart, loosen the lens that is often held in place with a dab of glue on the thread / mount, once that is dont you just need to turn the lens a few degrees in the correct direction.
What is the right direction i do not know, so you will have to just adjust a little them film some and then inspect that footage.
On newer systems with a wifi preview you can often use that to see the live feed, but old cameras at best had a AV out but this is not ideal for focus as this AV signal was low resolution.
Very few cameras in the old days also had a HDMI out, but i can not recall if the 0906 which i tested back in the day had this feature.
The 0906 system are pretty old stuff, modern systems will blow it right out of the water on just about any parameter.