Stop and look
A turret lets one sensor look in many directions. Drive until a wall is close ahead, stop, then swing the turret right, then left, and note what you see. Ahead you already know. Wait a moment after each swing so the sensor settles.
Used in mission: 3, 4Open or blocked?
A gap is not about how deep it is. Measure how far a side wall is when you are centred. Anything clearly farther than about one lane width is open. A tight U-turn is only a lane or so deep — judge it by depth and it looks like a dead end. Judge it by open or blocked and it is just a way through.
Used in mission: 3, 5The right-hand rule
Keep your right hand on the wall. At every junction: right open? Go right. Else straight if it is open. Else left. Else turn around. It finds the exit of any maze without loops. Contests such as Micromouse and RoboCup Junior rescue mazes start from wall-following like this.
Used in mission: 3, 4, 5, 7Dead ends: everything blocked
You do not need to guess a dead end from depth. Look in every direction. At a U-turn one side is open. At a dead end right, left and ahead are all blocked. Then turn around and carry on with the same rule.
Used in mission: 5, 7Remember your route
Robots keep notes. Add a letter to a list at every decision. Afterwards the list is the route: RLRL. Run the maze mirrored and it reads LRLR — proof the car is sensing, not counting.
Used in mission: 4Follow the line
Drive along the edge of the tape, not its middle. The sensor reads white high, black low, and the edge is in between. Proportional steering: steer in proportion to the difference — the bigger the error, the bigger the steer. Line-follower maze contests use this all the time.
Used in mission: 6, 7Green means go
Robots use coloured marks as signals: a finish tile, a doorway, a turn marker (RoboCup Junior line mazes use green squares). Your belly color sensor reads them without stopping the car.
Used in missions: allExplore, then sprint
Top maze robots run twice. The first run explores and records the route. They throw out dead ends, then the second run sprints the shortest path. Micromouse machines use a flood-fill map for this. Your route list is a great start.
Used in mission: 7Remember: the rule is more important than the map. If your car senses properly, the same program works in a maze you have never seen — even a mirror image.