YES
Depends on what type of vent system water heater has.
B-vent pipe.
When you cannot use B vent to find a way to vent the HWT through to the roof!
a direct vent water heater is more fuel efficient (cost's less to operate). aside from that there isn't much difference, aside from not needing a double wall flue through the roof on a standard gas water heater.
In plumbing the roof vent should be a min of 4" to prevent hoarfrost
Because of the carbon monoxide produced from the burner at the bottom that would build up and kill you.
You should not have to clean a vent on the roof. unless you are trying to clean the waste line to the fixture below. Then you would send plumbing rods through the vent on the roof.
Yes. The roof vent is usally located on the roof. If the vent is clogged, it can create numerous issues and prevent your plumbing system from working properly.
heater vent will not readjust to any position
I'm not 100% sure if they are to do with the moon roof, but if you pull out the right rear heater/air con vent (behind the driver) there are two 20A fuses. Maybe one of these are part of the motor.
A vent Terminal and depending if the roof is strictly for weather protection it terminates about 24" above the roof. If the roof area is for people then it is 7 ft above the roofing surface.
Yes you can get a high wind cap for the vent.