Technically, yes. You'll have to mount strip wood on top of this and mount the roofing to those same strips and make sure you use gasketted roofing screws. Personally, I'd go with a different, higher gauge product if this is a roof for your house. Is a little thin and I could see it denting pretty easily.
No only the Mill finish is available.
Yes They are galvanized but, anywhere they are scratched or cut they will rust. They will not rust for many years but, even galvanized metal will rust in time.
This is designed as a roofing panel. I have seen this used for ceilings. Not sure about the vapor barrier. You would need to check local codes for this.
It depends on the store. They can also be special ordered if your store does not carry.
My local store told me "no, we only cut wood". I used a trick I found online to use my circular saw and flip the wood blade over so it's cutting backward. That way I didn't have to spend $40 on a metal blade. Worked well.
It is the reverse issue of 2x4 size. The panel is actually 26” but due to the needed overlap, when you place the second panel on the roof, you only add 24” to the roof. One panel 26”, two panels 50”, three panels 74”
I know it is light in weight, I am 69 and can handle it with no problem