Underfloor heating noob questions

[Cheetah Designs]

I've only ever had electric heating before so have some noob questions.

Each floor has a manifold which has a pump. On the pump there is a button that I believe lets me cycle between 3 power settings. If I have the heating turn-on on the ground floor, the pump on every floor starts going.

Question 1:
I get that this is pumping the water but I'm unable to connect the dots as to why the pump starts on every floor even though the heating is off on those floors.

Question 2:
Setting the higher pump setting, does that mean the water flows through the underfloor heating more quickly and therefore heats up more quickly?

On the manifold there is also a temperature knob 30 -> 60

Question 3:
How does this link to what the boiler is doing/set to? Is it keeping the temperature of the water to the manifold (but not the heating) constant to that temperature even with the heating off and therefore wastful?

Question 4:
Perhaps this question is too open-ended. We have a well insulated house, what should the various settings be set to on each floor?