The shades retract by a spring pulling the inner cords. The maximum height is the one fold , so it is about 9".
These shades have a liner and block some light but it is hard for me to advise if it will be "enough". They are not room darkening shades.
This fabric is made of 72% Polyester, 28% Rayon.
Yes, the shades filter light.
No, this product can not be adjusted in length.
The reverse has a white light filtering liner for privacy and enhanced light filtration.
The shade including the brackets will be 31" , the fabric will be the same width as the roller which will be 1/2" narrower then the overall shade including the brackets ( 30.5") If you are inside mounting you must order a shade 1/4" narrower than your window opening for ease of installation and operation.
Yes ,it can be mounted on a door.
This is a standard length if you would like shorter you would have to move to a product that is custom.
They are not adjustable. The next wider size available is 35".