some questions about LPG piping

EngEsmail

I have some questions that I could not find answer for them, could someone help me please.
1. I read NFPA 58 and NFPA 54 for LPG piping, I read a regulation for LPG piping which said NFPA 58 is for out of building piping while inside NFPA 54 there is some Tables which is for 1st regulator to 2nd regulator!
2. In NFPA 54 there are some Tables for (1st regulator (10 psi) to 2nd regulator (2psi) with 1 psi pressure drop) and (1st regulator to 2nd regulator with 3 psi pressure drop). How could we find which one must be used? how could I calculate pressure drop for a house, or for a building or for a bakery?
3. there are some tables for 2psi service and line pressure regulator. and there are some table for 2nd regulator and appliance. I confused, it must be 1st, 2nd, and 3rd regulators, why it is 1st to 2nd, 2psi to line pressure, and again 2nd to appliance?! how many regulators are essential for piping of an house, or bakery, or an apartment?
4. the output pressure of the last regulator which deliver gas to the appliances of a house must be how much?

hot_rod

The very first number you need us the total BTU load of every appliance you intend to operate

Regulator options  and pipe  sizing can then be determined

EngEsmail

Thank you @hot_rod for your respond
Let me give you two example, one total BTU load of 350000 BTU/h for a house (the endpoint is 30m from 2nd reg. and 40m from the tank storage), the second example is total BTU load of 3500000 BTU/h for an hospital (the endpoint is 150m from 2nd reg. and 200m from the tank storage).

hot_rod

Are these buildings already piped inside? Or a new installation. I think 2 stage regulate more accuratly. It allows smaller tube size from the tank to second stage.

EngEsmail

they are not piped so far.