Depends on the sort of BLDC - if its a sensorless like all the RC ones then reversing direction isn't viable. Hall-sensor BLDC is needed for that if brushless is a requirement.
For specifications of a motor you look at the motor specifications. Simple. -
[ edit: Actually it helps to know about the relationship between Kv (voltage constant) and torque constant. This is trivial in SI but noone quotes Kv in SI alas (radians per second per volt). The torque constant (newton-metres-per-amp) times Kv = 1 (for an efficient motor). Thus a motor with Kv = 1800 rpm/volt (188 rad/s/V) has torque constant of 5.3mNm ]