For the purpose of the 'almost flat' side, a 10" wheel is 'almost flat' if you're working on something that is only half an inch wide.
Yes, you can. However, tool steel is so cheap that the savings in cost does not justify the additional work. Functionally, there is no reason to do this on a razor. You'd do it only for aesthetical purposes (or being historically accurate, but you'd use different steel) on things like razors.