Yeah. You did. The Final Battle (The Graveyard) can only be accessed in Single Player on a difficulty of 10 or higher after conquering the planet. It's not just the SNES version either that has this requirement. Most of the home console ports (not including the handheld ports which differ greatly) require you to play single player on difficulty 10 or higher. The PS1 version is one of the few where you can access it on any difficulty. (you still have to play single player though.) The arcade version also allows this as well iirc.
Edit: Also noticed you're missing Talon's and Chaos' stages just now.
Edit: Also noticed you're missing Talon's and Chaos' stages just now.