It certainly can. Because it is a raw wood, you will definitely want to sand it and use a primer or sealer on the wood before applying the paint. It will probably take a couple of coats to get a good solid white.
There are grooves on the back side.
I stained this product with a stain called General Finish. It stained beautifully. I was happy the way it turned out.
search for pictures of "Shou Sugi Ban" to see what I believe the asker was trying to communicate. It's a Japanese finishing method, of quickly torching the wood to create a charred, bugproof, somewhat weather resistant finish.
I don't know about both sides supposed to be smooth, but the purpose, as I understand, is for the grooved side to give a beadboard look/option.
This is a veneer covering not suitable for structural support. If you anchored through it to a stud it would work, but you would wasting the product behind the cabinets.
It is tongue and groove and we installed it over textured ceilings.
These store well if you laid flat. I would also recommend storing these in an area that has low moisture to avoid warping.
for soofitts 9x20
By "kit" I assume you mean one box. One box contains three packages of six planks each for a total of 18 planks per box.