yes you can.
could be either depending on the manufacturer, you should measure it in person to be sure.
yes this will work.
yes you can do that.
I think not. When I bought 12 of them, they were 12 in a bundle. When I bought 11 of them earlier this year, it was 11 loose pieces.
Yes you could, if your planer accepts the size
No, they are very easy to cut. I pretty much always cut them by hand in my mitre box
to my knowledge no chemical is used
Yes, I have used them for that purpose. I just use a hatchet to 'sharpen' the end of the board that goes into the ground. They work great for tomatoes and all, as long as the board doesnt have a large knot in it which is a weak point.