Rare. This is a rare phenomenon. If you are concerned then you should visit a sports medicine specialist to evaluate you. Many times when it the muscle heal, there may be fibrosis in the area of the defect.
6-10 weeks. 6-10 weeks.
No easy answer. This will take time since this will need to heal on its own. In the beginning the principle of rice (rest, ice, compression, elevation) are mandatory. Make sure that you keep range of motion in your ankle and knee. Over stretching the calf will just continue to reinjure the muscle.
6-12 weeks. 6-12 weeks depending on location of muscle. Initial rest and possible immobilization is recommended. Then re-evaluation by your dr. Or pt to start rehab.