I need some pages to be accessible only by the not-authenticated visitors. How can i do that?
Guest role does not seem to work nor do i actually know for what this guest is for.
Guest role is for non-authed users. It's probably working but because you're an admin you can't tell.
I've just pushed a patch to fix that testing case as I've done in Navigation in the past. Should reflect the guest restriction properly now to admins.