068,
It appears to me you have 4 pipes feeding your pump, not counting your spa input..
I suspect that the pipes go to skimmer 1, skimmer 2, main drain, and the pipe on the end without a valve is your suction side cleaner... But that is just a guess as no one can tell you what each pipe does for sure, as there is no universal way to do it..
You will just have to use common sense and experiment and see what you find out..
Point the handle of all three intake valves straight down.. This will result in all 4 pipes being wide open..
Then... starting with the manual valve next to your automated valve, turn the handle of the first valve so that the handle points straight up.. This will shut off the pipe directly below the valve..
Now go out and see what is not working.. Remove the skimmer basket and feel the suction.. If the suction in one of the skimmers is off you will then know what valve controls what skimmer
I suspect that the last valve in your set up has the main drain coming into the bottom of the valve and the suction cleaner comes into the side.. If that is true, then shutting off most of the main drain, will open most of the cleaner.
Thanks,
Jim R.