Per the NCAA rules book for women’s and men’s volleyball, the libero is strictly a back-row player and can only be replaced by the same player it replaces. Also, a coach can only designate one libero per set.
For most teams, the libero is not a starter. At the beginning of matches before the first serve, the libero will normally replace a player in the starting lineup. That player becomes the only player that can replace the libero. (There is normally one official tracking the libero substitutions during a match.)
The libero, also according to the rules, cannot “complete an attack hit” if the ball is above the net and it cannot perform an overhead set in front of the attack line — commonly called the 10-foot line — while still having teammates attack the ball above the net.
Officiating CVB sounds like a tough assignment
For most teams, the libero is not a starter. At the beginning of matches before the first serve, the libero will normally replace a player in the starting lineup. That player becomes the only player that can replace the libero. (There is normally one official tracking the libero substitutions during a match.)
The libero, also according to the rules, cannot “complete an attack hit” if the ball is above the net and it cannot perform an overhead set in front of the attack line — commonly called the 10-foot line — while still having teammates attack the ball above the net.
Officiating CVB sounds like a tough assignment