In all the talk of graphical downgrades no one seems much preoccupied with 'why?'. Why build something and then proceed to tear it down, piece by piece, in the hope that ever more diminished expectations about the final product won't be severe enough to...
If something looks like it's important, give it a tap. Chances are that it is.
You can replay the arcade games you've found whenever you want from the menu.
There's a map on most of the screens that shows you exactly where you are.