Yes, this is the first one! That’s a great question that I haven’t quite figured out yet, though I know I need to.
Currently each bonus puzzle is its own page, but I’m thinking of integrating them into the normal navigation, after Sunday’s puzzle, but only once you unlock them via the link from the newsletter. So maybe that can unlock all past bonuses as well?
(This whole scheme can be “hacked”, but if someone cares enough to go to that much trouble but really doesn’t want to sign up for the newsletter, knock yourself out! It’s just for fun.)