Yes! Over exercise & do not allowing your body time to repair itself, can lead to muscle breakdown (rhabdomyolysis), rather than buildig muscle. Also, if you are not eating properly for the amount of exercise you are doing, you can damage your body by burning too many calories that body needs to do everyday functions. It also puts you at risk for muscle & joint injuries. Make sure to rest & eat enough.
DEFINITELY! Just as important as the exercise is the rest. Exercises cause microscopic damage to occur. The physiologic benefit of exercise occurs as the microscopic injuries heal. The healing process requires time, rest, and appropriate nutrition. If you overdo it, you are setting yourself up for decreased performance and potential injury.
Switch it up. If you do the same exercise over and over, you risk overuse injuries and stress fractures. Vary your routine. Since your name is andrew, I assume you are male. Girls are different, lost period=lost bone.
Exercise. Yes, overuse can lead to muscle tears, stress fracture, ligament tears, among others. Vary your length, intensity, and muscle group.