Basic Libero questions (very basic)
 

A team shows up with only 6 players.
Can they use a Libero?
If so What happens when the Libero in position 5 needs to roatate to 4 and there is no replacement because they have only 6 players present?

No, they cannot play with a libero. They would need to have 7 players to use a libero, as the libero REPLACES a backrow player an unlimited number of times. This is not the same as a SUBSTITUTION.

Thank you.
and on a rotation when the 2 position rotates to the 1, can the Libero replace that person and serve?

my recollection is that the libero can replace the server and serve in that one spot only for the entire game.

Receiving team has 7 players. The Libero is in position 5. They win the rally. The Libero stays in 5 and the player in 6 rotates to 4. Illegal?

clarification: Receiving team has 7 players present. 6 on the court, 1 on the bench.

This is an illegal replacement. The libero may replace the server (position 1) if they have not served in any other rotation, otherwise, the libero must leave the court for one completed rally and the player replaced in position 5 must reenter the court in position 4. The player in position 6 will rotate to position 5.

This. Even without the libero replacement mess, a non-libero in position 6 will always have to rotate to 5.