How do I make separate saves for different parts of one game?
I want to make the game consisting of three parts both by the plot and by the gameplay. I'm going to use a persistent variable to go from one part to another, it's already in use for main menu's background and for the label to start when the game is starting, but I'm afraid that save system might break if some player go from 3 to 1, for example. Is there a way to make certain save slots uninteractable (when you at 2, you can't go to 3 without progress or 1 without reset) or make three save lists to switch between them safely (each new part starting with forced save at the end of previous one)? Or maybe I heavily overthinking it and there's another option that isn't that critical to whole system?
Edit: Also I would appreciate any advice about autoupdate buttons on the main menu, because background do change while in game, but buttons require to reload T-T