What mode is vim in when I press a single 'r' and is it possible to have a mapping here?

Question

For a quick overview, I map to so I can more easily cancel out of things without moving my hand to the escape key. For exam

Answer 1

If you find you've accidentally pressed r, how about just tapping uu?

This will make the replacement but immediately undo it again, without you having to move your hands from the letter keys.