Upgrading an Old Mac Mini

I am trying to upgrade an old Mac Mini that I have had sitting around for a while.
Apple upgrade are cumulative and slow, you need to finish one before the next will be allowed.

Just found a strange option. The upgraded mac required me to slow down the monitors refresh rate, otherwise it would not turn the screen on. Currently it has reach version 10, but I need to get it to 12.5

It’s a 2 hour reboot cycle, when it can find a screen.