1/2 inch copper/plastic pipe is standard for water
2" water main then the branches are sized to properly supply fixture unit demand with out excessive velocity which can cause erosion and hydraulic shock
No, water expands in size when frozen. That's why ice floats on water, and why pipe bursts occur when trapped water in them freezes.
1"
Check pipe size for hot water or if galvanized pipe used, pipe could be clogged inside with rust and scale.
1/2 in. pipe commining to it and then you could bring it down to 3/8 pipe
A lot less because the water is flowing if it is exiting and it depends on the water pipe size.
Depends on how much is flowing into the pipe. One bathroom sink, 1 1/4"
Depends what size your pipe is
0.255 gallons per foot of pipe. A 10 ft long pipe that size holds 2.55 gallons.
The pressure will rise, but you haven't given us anyvolume or pressure figures to begin with .
Depends on the size of the heater Commerical etc
For a 200amp service you need number 4 copper
Trey sharkbite coupler if it is on a straight pipe. Use a good pipe cutter the size of your pipe. Plug in the coupler. It does not require any soldering. Check for the you tube video.