Undo Button

I am working on a role playing game in which a player's actions affect a stat sheet, similar to D&D or any of the role playing games where there's a skill tree and xp awarded to it. 

If a player mistakenly clicks on an option, i want them to be able to have a way of undoing their last step. I don't really want to give players the chance to click back and forth testing out how each action would affect their stats sheet but i do want to, for accessibility's sake, have folks be able to undo mistakenly clicking on an action. 

Do you think it would be better to build some kind of undo function or have each action bring up a "Confirm" button making it so they have to click twice for every action. I personally would probably find that annoying but it's the easier thing to build, i suspect. 

If i were to go the route of building an undo function, i'd need it to not only go back to the slide before - which was randomly brought up out of a pool of 40 slides, but also undo the +1 / -1 to all the stats on the stat sheet. Is that even possible?