I have aq uick question about bicycles relating to physics. I hope you can understand this!

Question

First (technical question) why don't bikes move backward when you pedal backward?

On to the physics. A string is tied to a bike enabling one to pull the pedal from the down position (so that the pedals are turining in a clockwise fashion instead of counter clockwise) from in front of the bike. The bike moves forward. Why does this occur?

My answer involved the force (and torque) being large and in the direction forward where the bike would move. Any friction from the gears, etc. would be overcome.

Some bikes can go backwards...I am thinking of the bikes used by acrobatics on circus high wires.

Normal bikes cant petal backwards because of a clutch that allows the rear wheel to turn faster than the pedals.

The string on the petal is mechanically linked (string, petal, chain, rear wheel hub, rear wheel) to the rear wheel which moves the bike forward.

is the front of the bycycle facing lerf or right?