(1) Yes, displacement can be zero even if a body has covered some distance. (2) When a body travels in circular path , after covering a circle the distance cannot be zero,but its displacement is zero. (3) By calculating the slope from the graph speed of the body can be calculated. (4) Yes, an object can have zero velocity and still be accelerating simultaneously. Example: When the body is projected vertically up, at the highest point its speed becomes zero whereas it is accelerating downwards with g = 9.8 m/s2. (5) No, it is not possible.