Sacrament of Holy Spirit? The sacrament by which members of the church are ordained for percent ministry in the church as bishops, priests, or deacons.
Despite his human failing, by God's grace, Peter was forgiven, and was given the keys to the kingdom of heaven. After Peter professions Jesus to be "the Messia" The keys to signifies Peter's authorities to govern the church.
Despite Peter fallibility in Jesus, Jesus chose him to be a solid rock of the church. If God can make use of Peter with all his weaknesses, that means we still have hope because we are not perfect humans like his Son.