Forums → Game Walkthroughs → Stuck on Sonny 2 level...

You have to play the game on I think challenging or heroic difficuluty

You have to play on heroic difficulty AND not repeat ANY boss battles OR training battles

Zone 6 is available on Challenging or Heroic after merely defeating the Mayor.

Zone 7 is available once you get the Legend achievement. Once you have that, you can access Zone 7 any time you play on Heroic regardless of training battle use.