I have a 3rd function kit that I'll soon be installing on my 2538HST. Someone was nice enough on this site earlier to tell me the power beyond port is the one that has the longer fitting on top of the control valve. And yes that's the one that then goes to the hydraulics at the rear of the tractor. I'll let you know how it goes.
Also, if anyone is interested, I have just completed installing the cruise control kit on my tractor that Mahindra sells. It was a very easy install and works great. All connections and brackets were existing on the tractor and took longer to locate them than to do the install. The entire job took less than 30 minutes, and that's with knowing nothing about the kit and installation since no instructions are included. You only have to take out the three dash panel bolts and you can get behind it enough to install the new push button switch.
It holds the forward pedal by a electrically energized magnet and like the automotive styles, it disconnects by pressing the switch again or the brake pedal.
The Cruise Control Kit for the 2538HST was part # 12386210000