Studies of Euler diagrams/gap variants/medusa

(without spot 3)
Spot 3 is one of the octants of the 3-split ABC. Without it, it disappears.

(without spots 2, 3)
Without these two adjacent spots, both 3-splits (ABC and BCD) lose their bottom front octant, and disappear. Only the six 2-splits are left.

(without spots 0, 2, 4, 6)
Without these four adjacent spots, the 2-split AD loses its quadrant on the right. It disappears, and the two borders A and D are now parallel. The only fullspot in the overlap of A and D is 9. But the 2-split BC requires four quadrants in each of the three AD regions. The missing three quadrants besides 9 are the gapspots 11, 13 and 15. The shape is like that of.