The Side B Sagittarius Riddle requirement is as follows -
"Got three "Spinny!" in "Inside"".
Inside is the second to last level in the game, and about 15% through it, you'll come to a tunnel that you can spin around in. Spinny is doing one full 360 spin in this tunnel, either going left, or right. You can do about 1-2 spinnys before the electric fences, then do one more after them once the tunnel is nearly at an end.