I would not recommend using this without some other structure to support it. This is designed to lay on a subfloor and doesn't have enough strength to support standing on. You could probably use it on wall framing but not on the floor by itself. I am able to bend and break the 1/4 board with my hands.
Absolutely. Just make sure you anchor into the studs. I do this same thing regularly. Good luck and have fun, Jim G
If im understandingthe question correctly you are talking about the inside of the cabinet. the backer is not water proof. Replace it and caulk with silicone
Yes of course.
Yes You can use it but Use 1/2 inch
Yes! However it may void any warranty. I have done this several times.
No it makes no sense.
Yes. I installed mine directly on to the studs and laid the rock.