1. Highly unlikely the ESC caused a mechanical lockup in the motor.
2. Any number of mechanical failures in a motor can generate substantial heat....and often result in instantaneous or short term intervals of high current draw which can heat up both the motor and ESC.
3. Very hard to say. If it programs ok, does not smell, does not have any melted heatshrink or charred marks, it is probably ok. In my experience, if the ESC is not ok, it is unlikely it would cause damage to a functioning motor; it just won't run the motor properly (if at all).