A acceleration never changes, So the object will never stop changing. ... For positive, the object will move towards right and for negative case, it can move towards left direction.

At what times does the object change direction?

The object switches direction when v = 0.

How do you know if an object has change position?

changes position requires a point of reference. An object changes position if it moves relative to a reference point. To visualize this, picture yourself competing in a 100-m dash.