With a simple pool, and no spa, it's often possible to tell what the valves are, just by looking at the the equipment. But, I can't make it out without testing, in a more complex situation.

My recommendation would be to try to find, and hire, a decent local service guy, have him puzzle it out and then show you. If that's a DE or cartridge filter, you also need to have him show you how to open and clean those filters.

-- Do NOT acid wash or clean those filters -- read the cartridge filter sticky in this section --