1. You got it right.
4π/9 x 180/π = 80°
2. To get a coterminal angle you start with your angle and then you add or subtract 360° (one cycle around the circle).
-123+360+360 = 597°
-123-360 = -483°
3. The angle is 215° from the point (1,0) on the unit circle. The angle 215° is between 180° and 270° so it is in quadrant 3.