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.
I could not say with certainly, other than no I didn't have to do it for my bathroom. Whether I should have,,,, MDF does have some serious problems to overcome but make sure you keep it flat. It will both warp and separate at the ends. What a lot of people don"t know is that if you seal the exposed ends with something, even glue you will keep the moister out.
The boards naturally stagger at a nickel gap so you don't have to do any guess work. These are the ones you use when you want the nickel gap-not a seamless look. They make the job SO easy! LOVED THEM! :)