This gearmotor is a miniature high-power, 6 V brushed DC motor with a 986.41:1 metal gearbox, making it a great choice for applications requiring fine…
In terms of changing the polarity of the power supply to cause the motor to rotate clockwise and anticlockwise, yes, the gearing is agnostic to the direction of rotation, you can turn it both ways.
However, I’d suggest avoiding turning the motor by applying a force to the shaft, the high ratio may cause damage to the motor if you overdrive it in reverse (although this is quite typical for any geared motor)