Question

if we stop pedaling the bicycle during its ride why the bicycle slows and then stop​

Answer 1

it slows down because of frictional force that opposes the motion of the bicycle. The bicycle slows down because of the frictional force acting on the tyres of the bicycle.

Answer 2

When the rider stops pedalling the bicycle, the force of friction between the tyres of bicycle and the road acting in the direction opposite to the direction of motion of the bicycle, opposes the motion of the bicycle and this force is now unbalanced, thus slowing down the bicycle