Yes. Each undo adds one step to your score, and Reset adds one for every step it clears, so backing out of a dead end is never free.
Yes. Undo and Reset both work before you submit, but each use is counted.
What it costs
- Undo removes your last step and adds one step to your score.
- Reset clears every step and adds one step for each step cleared, as if you had pressed Undo repeatedly.
The cost applies to your final score even when the undone step was not part of your best route. Two players who find the same number are ranked by steps, so an undone mistake can be the difference between them.
Is it still worth using?
Often, yes. A wrong route costs a step; getting stuck and finishing further from the target costs more, because distance is ranked first. Plan the route before you commit, as the strategy guide recommends.
The server replays the undos as well as the steps, so they cannot be hidden. A log holds at most 40 actions, steps and undos together.