Pilate was the Roman governor of Judea at the time of Jesus' ministry and Barabbas was a convicted murder. Pilate offered to release either Jesus or Barabbas assuming the crowd would respond reasonably and ask for Jesus' release. The mob chose Barabbas, and they called for Jesus to be crucified (Luke 23).
Yes Pontius Pilate was the governor , so he had all power to question, sentence to death or release a person, he questioned Jesus.
The most common from of release from prison is discretionary parole. This is the release of an inmate from prison to supervision that is decided by a perole board or other authority.
Passion Play Christ Before Pilate and the Condemnation - 1903 was released on: USA: January 1903
Pilate
Barabbas
If you read John 19:10 this will help you to see that Jesus knew full well that Pilate had the authority to release him or put him to death. Ultimately Jesus was condemned and executed at the hand or order of Pilate.
The Jews asked for Barabbas to be released. Luke 23:18-19 tells us that, "The whole crowd shouted, "Away with this man! Release Barabbas to us!" (Barabbas had been thrown into prison for an insurrection in the city, and for murder.)" (NIV)
Studio One - 1948 Pontius Pilate 4-30 was released on: USA: 7 April 1952
The robber released in Jesus place was a man called barabas.
Mk:15:14: Then Pilate said unto them, Why, what evil hath he done? And they cried out the more exceedingly, Crucify him. Mt:27:17: Therefore when they were gathered together, Pilate said unto them, Whom will ye that I release unto you? Barabbas, or Jesus which is called Christ? Lk:23:4: Then said Pilate to the chief priests and to the people, I find no fault in this man.
Pilate was not Emperor, he was Governor.