That's fascinating, I've never seen the early version before - Robotnik is 95% the Saturday cartoon version, but with long sleeves (like the Spinball concept art) instead of bare arms and smaller shoulder pads. A shame Sonic's ear gets in the way, so we can't see whether the robotic arm had been established yet. Sonic's mohawk spines also have a DiC-like quality to them. That more or less clears up the mystery of why Robotnik looks the way he does on the cover - he was the DiC version (or a slightly earlier incarnation), then his face was edited into the western game version. His outfit in the interior comic (and the early newspapers strips/STC) is still a mystery though - the other artists just drew the game version. The Yearbook was released summer 1993, so I guess it was drawn mid-1992?