Option 1: This statement is correct. When velocity and acceleration have opposite signs, it means the object is changing direction, which typically indicates a slowing down or deceleration.

Option 2: This statement is not correct. At an instant where velocity is zero, the object can still have non-zero acceleration. For example, a ball thrown upwards will momentarily come to rest at its maximum height, but it still experiences acceleration due to gravity.

Option 3: This statement is also not correct. If the velocity is zero for a time interval, it means the object is momentarily at rest. However, the acceleration can still be non-zero during that time interval. For example, a car at a traffic light has zero velocity, but it experiences acceleration when the light turns green.

Option 4: This statement is correct. When the position and velocity have opposite signs, it means the object is moving towards the origin or the starting point. For example, if a car initially moves away from the starting point and then starts moving back towards it, the position and velocity will have opposite signs.

In conclusion, the incorrect statement is Option 2; if velocity is zero at an instant, acceleration can still be non-zero.