The Alpine manual and update data was available on their website last time I looked
Owners manual is OM_INE-W920R_UK.pdf
The correct update zip file is FU_INE-W920R-1-3.zip
Getting it to show the correct picture took me a while because of not understanding Alpine’s odd logic in switching and muting the various possible video inputs.
In essence you must use the “Direct” connector, it needs a small hard-to-source 5pin plug to the socket taped onto the loom coming immediately from the head unit.
The other significant problem is how you take the video from the blanking plate in the boot lid between the two numberplate lights all the way through to the back of the Alpine, unless you use an rf link.
I did it in two bites, first and easiest one as with my old Niseko and using the Garmin as the display.
Having learned from this I later rewired the boot-lid umbilical to take both video and reverse power.
Elsewhere earlier on that thread are a lot of sidetracks about wrestling with the Alpine
Then install the connector to the Alpine
I have an unused rf link left over which I never tried.