The supplement was actually released in the UK (in English). I own it and was meant to scan it (but don't have a scanner any more).
It uses Sonic 2 sprites for all of the screens and there's a few new Sonic 2 sprites made just for the game.
It also looks back at the history of the Sonic games (up to Sonic 3). According to it Sonic CD had a different working name (I don't have the supplement at hand, so I can't remember the exact bame). There were some other interesting bits as well.