The V5 is the same as any other controller for the rpm input. Yes, the A5 pins is the Aux 5. The governor is not in the main code yet. But there is a thread here when it was introduced for user testing and it explains how to set it up.
3.6.5 is still a point release candidate #2, but I think it will be going to official point release soon. There is a link there to where you can download the binary with the governor (still built on 3.6.3). But I will update that today to 3.6.5 and make a post on that thread to indicate that the binary is available on the latest point release.