Hello - I will forever in your debt if someone can help me figure out the way my pool works.....

Just moved into home with Anthony & Sylvan in ground plaster pool. It has a D&E filter, a water purifier, two skimmmers, two bottom pool drains, and a return line for a polaris 360.

My problem is the valves on the pump. I'm not convinced that I have them set up properly.

When I have the pool drain and skimmers open, I get no pressure into the skimmers. Can I only run one at a time?

Should the pool cleaner valve (return line) be open when I run the skimmers or pool drain?

When operating the Polaris 360, my pressure goes from 12 to 25. Is that normal? The only way I can get it moving is to shut off the pool return drain completely. Should I use the eye-socket dealies to plug up the other return lines, instead of manually closing the pool drain return?

I apologize if I am being confusing. I have 4 valves on the pump - one for skimmers, one for pool drain to filter; one for pool cleaner, and one for pool drain return. My basic question is what do i open when.