Flexible...rubber with fabric covering I think.
Cheaper than 2 with out one it will roll
Unscrew the red plastic wing.
The valve to shut off the tank is a poor design. One thing I noticed is the plastic piece attached to the valve is easy to strip and then opening and closing is a problem. I finally broke off the plastic and used plyers to open and close the valve.
It depends on the size of the tire and how much air is in the tire. It does a regular tire on a car just fine. Adding air to a semi it does ok. You are not going to fill more than two flats on a car.
I would replace the whole assembly
The air pressure gauge is 1/8". The tank has a 1/2" hole. The air outlet hose is 1/4"
With the valve fully closed my tank held air for months.
Not long enough at the pressure you require without an air compressor attached.
A standard valve core remover will work just fine. Any auto store will have one.