First time building 2 storey home, is under construction (in Framing stage) in NSW.

I have 3 toilets and need bidet spray in each with legally installed (example images below).

Any plumbers in this group please advise.

1. How many RPZ (Reduced Pressure Zone) valve needs here. one in main water meter, one in each toilet so total 4 RPZ & cost?

2. Where and how all this RPZ valves are hidden but accessible for service. Please share the images.

3. How much the annual service cost for each RPZ or total system? How long needs to be serviced.