In a robotics competition, a robot is programmed to move in the coordinate grid to collect colored flags placed at various points. The robot starts at the origin \((0, 0)\), moves to the red flag at \((0, 3)\), then to the blue flag at \((-4, 3)\), and finally to the green flag at \((-4,-3 )\).
(i) Find out the quadrant in which blue flag is located.
(ii) How many units did the robot travel from red flag to blue flag?
(iii) What is the final position of the robot?
(iv) Which axis is crossed when moving from blue flag to green flag?