Whilst there is only one queen bee in a regnant (ruling) capacity her replacement will be alive and "waiting in the wings" to take over on her death or departure.
Two
Only one.
There is one queen, 200 to 300 drones (males), and 20,000 to 50,000 workers (all female)
In a honey bee hive, all of the bees are workers (infertile females, up to 80000), except for the queen and a few hundred drones (males).