Short answers, pulled from the story.
The Seal of Confession is the absolute obligation of Catholic priests not to reveal anything learned during the Sacrament of Penance. Anglican and Methodist traditions hold an equivalent seal; Church of England canon law explicitly charges ministers not to reveal at any time any crime or offence confessed to their trust and secrecy.
Catholic teaching requires contrition (genuine sorrow for sins committed), disclosure (the spoken confession of sins), and satisfaction (an act of penance assigned to make amends). The priest acts in persona Christi and the Council of Trent cited John 20:22-23 as the primary scriptural basis for the sacrament.
Orthodox Christian confession takes place not in a confessional box but in the main body of the church, before an analogion holding a Gospel Book and blessing cross. The penitent builds an ongoing relationship with a single spiritual guide called a spiritual father, often a parish priest or a starets, rather than confessing to any available priest.
Mutual Forgiveness is a rite in which the priest prostrates before the congregation and asks forgiveness for sins committed in act, word, deed, and thought, and the congregation then prostrates and asks the priest's forgiveness in return. The best-known occurrence takes place at Vespers on the Sunday of Forgiveness, marking the beginning of Great Lent.
In Islam, the act of seeking forgiveness is called Istighfar and is made directly to God with no clerical intermediary. Sins are to be kept private between the believer and God, with the only exception being when confessing to another person is required to repair actual harm done.
In the Alcoholics Anonymous Twelve-Step Program, confession appears as Step 5: admitting to God, to oneself, and to another human being the exact nature of one's wrongs. AA literature describes completing this step as obtaining complete forgiveness and warns that un-confessed wrongs will haunt a person and lead to the demise of body and spirit.