A - Use Superman's freeze breath to extinguish five LEGO fires around the third area (story)
B - Use Cyborg to manipulate the magnetic object near the third area's starting point, then solve the floor maze puzzle (free play)
C - After shutting off the electified area, use Poison Ivy to pass through the background vine patch (free play)
D - Citizen in peril: Fly up to the balcony above the third area's X-ray wall, then use the Batsuit's sonar gun to shatter the glass and trigger all three switches simultaneously (free play)