No, the circuit would do the necessarry pwm required by a servo. It is possible to make the H-bridge with other components other than the specified one, you just have to find one that you can get the components for.....
It can be made to work without a h-bridge but realistically the other components would overheat and die. The H-bridge is there to give power to the motors seperate from the rest of the circuit so the other components dont have to have the required energy for for the motor running through them
No, the circuit would'nt