Yes, you "can" but I would not. You would have to be sure to paint it with a weather proof, and I mean water and snow, proof paint and seal the nickel joints so that no moisture accumulates. This is an awful lot of work (and caulk) when you could just use cedar or vinyl siding
no you do not need to.
you can , but I wouldn't. It needs to move when it gets humid out.
A few pieces were flawed but all in all turned out well
This is finger jointed primed, not pressure treated lumber. It will not do well in a shower!
If the "steel studs" are the standard ones used in home construction which are flimsy and can be easily twisted...Nail gun. Use two nails placed about 3/4 to one inch apart angled towards each other so they form a V shape in the wall. The nails will 'pinch" to hold the board in place. You could also put a dab of liquid nails on each stud to hold the boards in place in case the nails loosen over time.
Coverage Area (sq. ft.) 5.25 ft² 225/ 5.25 = 42.85 so about 43 of these.
It depends on the look you want, and if it's in a corner or not. It will work if you just butt it up to it.