#2 Can this be used if the sprinkler heads are located higher than the valve?
Yes but there will be some back flow which is what the anti-
siphon valve part is for. I don’t have this exact brand but 4 of Champion brass valves that look very similar to it. I recommend that you instead get the ones with the union joint at the valve inlet, makes it much easier when maintenance is required. I have two of those valves.