Hoonbaba,
I'm sorry if I'm overdoing it with all the questions:
Does the Catholic Church teach that confession to a priest ABSOLUTELY necessary for forgiveness of sins?
As a precept of law for Baptized persons; yes.
Absolutely necessary though? Strictly speaking, no.
It is possible to have one's sins forgiven via perfect contrition (genuine, absolute sorrow before God, not simply because one fears what He'll do to them...much like being sorry only because you were caught, but sorry to the point you're sad you've offended God because He is good and Holy.)
However the problem is we have no capacity on our own to judge whether we're perfectly contrite or not. Unless God actually opens the clouds, and says to you "you're forgiven", you have no right to presume.
As a precept of law, for Baptized persons confession is required for the remission of serious (mortal) sins, which are seen as damaging a person's relationship to the Church, and destroying their relationship with God. None can be a "son of God" by grace, if they do the works of the "sons of satan". Confession of sins is the only way known to have any certainty about the remission of those sins if one is contrite (even if it's only imperfect contrition, the Sacrament is efficacious.)
Also, since it is the Church which is the steward and guardian of the Holy Mysteries, it must re-admit grievous sinners to the right standing to receive Holy Communion non-sacreligiously (which is what someone who has grievously sinned does; commit sacrelige.)
If that's true, then doesn't that contradict scripture, particularly where it says that Christ is our mediator of the new covenant? (1 Timothy 2:5, Hebrews 9:15)
For there is one God, and there is one mediator between God and men, the man Christ Jesus, (1 Timothy 2:5)
15 Therefore he is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred which redeems them from the transgressions under the first covenant. (Hebrews 9:15)
All either of those verses say is that the Lord Jesus, true God and true man, is the essential Mediator between God and mankind. Christ is the lynch pin without Whom there'd be no redemption; without His shed Blood there'd still be a "Cherub with a flaming sword" preventing men from being re-admitted to the Paradise.
That you see adominishments in the New Testament to "pray for one another" or to "confess one's sins to one another" should be proof enough that there is an agency through which grace is received, even if it is ultimatly merited and finds it's source in Christ Jesus.
Though Christ Himself is "the Teacher" in His own words, and hyperbolically He taught "call no other man teacher", what did He do after His Ressurection? He told the Apostles to go and "
teach all nations, baptizing them in the Name of the Father, and of the Son, and of the Holy Spirit". Indeed though it is Christ Who is "THE Lord", are there not other "lords"? Other "kings"?
Just as the efficacy of all earthly authority comes from the fact it relies on and is given by God (Who has all authority of Himself), so too all true Priesthood and Sacramental acts, and even all efficacious prayers, have their source in the Person of Christ as Mediator (being true God, and true man, and paying the debt for Adam's sin.)