You can put it at any height. Unless there is some other reason not to, something structural, I always put them above the shower stall for taller people.
above it in the wall
72 inches from tub floor.
Yes and what is the question?
If you wish to control the second head from the original shower control, then come off the head. That way both shower heads can be controlled from one location. Realize that the water pressure will decrease as they have a common source, which is normally a 1/2 inch line.
Shower spouts are usually 60 - 70 inches above the tub floor.
For aesthetic reasons, the shower head and taps are often in a line with the floor drain. I have never heard of any requirement that they must be so. It is usually most convenient to have the drain centered in the shower stall area, and the head is usually likewise centered, and a short run from the handles to the head is generally preferred, so yes, more or less.
The difference between a shower and a tub is the shower tends to enclosed with water that comes out of a shower head above while a tub has a faucet that pours into a large basin.
PVC pipe extension, that's what we did
Bath tubs don't necessarily contain a shower, and a shower may not have a bath tub. Shower tubs are a combination bathtub and shower; the shower head is usually mounted above the bath tub, allowing for bathing and shower drainage.
The ball connector is what the shower head rotates on to point the shower head in different directions
Yes, but only if you have a Rectal Thermatude Tramsmutor connected directly parallel to the shower, this will ensure that the oscillation period is reduced to 5 micro fliptons and at the same time will increase the static radial coupling on the thermal housing unit.
The shower head has a device installed that reduces the volume of water that passes through the orifice plate. It does not matter how much the shower head tap is turned up there will only be a specific amount of water that gets past the orifice plate, hence saving water.