The questions posed in the original thread are certainly interesting, as well as quite important to Catholc theology, to say the least. Since we are only discussing the Catholic faith, I will simply quote below the relevant sections of the Catechism of the Catholic Church which pertain to the questions posed:
Catechism of the Catholic Church:
The episcopal college and its head, the Pope
880 When Christ instituted the Twelve, "he constituted [them] in the form of a college or permanent assembly, at the head of which he placed Peter, chosen from among them."
398 Just as "by the Lord's institution, St. Peter and the rest of the apostles constitute a single apostolic college, so in like fashion the Roman Pontiff, Peter's successor, and the bishops, the successors of the apostles, are related with and united to one another."
399
881 The Lord made Simon alone, whom he named Peter, the "rock" of his Church. He gave him the keys of his Church and instituted him shepherd of the whole flock.
400 "The office of binding and loosing which was given to Peter was also assigned to the college of apostles united to its head."
401 This pastoral office of Peter and the other apostles belongs to the Church's very foundation and is continued by the bishops under the primacy of the Pope.
882 The Pope, Bishop of Rome and Peter's successor, "is the perpetual and visible source and foundation of the unity both of the bishops and of the whole company of the faithful."
402 "For the Roman Pontiff, by reason of his office as Vicar of Christ, and as pastor of the entire Church has full, supreme, and universal power over the whole Church, a power which he can always exercise unhindered."
403
883 "The college or body of bishops has no authority unless united with the Roman Pontiff, Peter's successor, as its head." As such, this college has "supreme and full authority over the universal Church; but this power cannot be exercised without the agreement of the Roman Pontiff."
404
884 "The college of bishops exercises power over the universal Church in a solemn manner in an ecumenical council."
405 But "there never is an ecumenical council which is not confirmed or at least recognized as such by Peter's successor."
406
885 "This college, in so far as it is composed of many members, is the expression of the variety and universality of the People of God; and of the unity of the flock of Christ, in so far as it is assembled under one head."
407
886 "The individual bishops are the visible source and foundation of unity in their own particular Churches."
408 As such, they "exercise their pastoral office over the portion of the People of God assigned to them,"
409 assisted by priests and deacons. But, as a member of the episcopal college, each bishop shares in the concern for all the Churches.
410 The bishops exercise this care first "by ruling well their own Churches as portions of the universal Church," and so contributing "to the welfare of the whole Mystical Body, which, from another point of view, is a corporate body of Churches."
411 They extend it especially to the poor,
412 to those persecuted for the faith, as well as to missionaries who are working throughout the world.
887 Neighboring particular Churches who share the same culture form ecclesiastical provinces or larger groupings called patriarchates or regions.
413 The bishops of these groupings can meet in synods or provincial councils. "In a like fashion, the episcopal conferences at the present time are in a position to contribute in many and fruitful ways to the concrete realization of the collegiate spirit."
414
The teaching office
888 Bishops, with priests as co-workers, have as their first task "to preach the Gospel of God to all men," in keeping with the Lord's command.
415 They are "heralds of faith, who draw new disciples to Christ; they are authentic teachers" of the apostolic faith "endowed with the authority of Christ."
416
889 In order to preserve the Church in the purity of the faith handed on by the apostles, Christ who is the Truth willed to confer on her a share in his own infallibility. By a "supernatural sense of faith" the People of God, under the guidance of the Church's living Magisterium, "unfailingly adheres to this faith."
417
890 The mission of the Magisterium is linked to the definitive nature of the covenant established by God with his people in Christ. It is this Magisterium's task to preserve God's people from deviations and defections and to guarantee them the objective possibility of professing the true faith without error. Thus, the pastoral duty of the Magisterium is aimed at seeing to it that the People of God abides in the truth that liberates. To fulfill this service, Christ endowed the Church's shepherds with the charism of infallibility in matters of faith and morals. the exercise of this charism takes several forms:
891 "The Roman Pontiff, head of the college of bishops, enjoys this infallibility in virtue of his office, when, as supreme pastor and teacher of all the faithful - who confirms his brethren in the faith he proclaims by a definitive act a doctrine pertaining to faith or morals.... the infallibility promised to the Church is also present in the body of bishops when, together with Peter's successor, they exercise the supreme Magisterium," above all in an Ecumenical Council.
418 When the Church through its supreme Magisterium proposes a doctrine "for belief as being divinely revealed,"
419 and as the teaching of Christ, the definitions "must be adhered to with the obedience of faith."
420 This infallibility extends as far as the deposit of divine Revelation itself.
421
892 Divine assistance is also given to the successors of the apostles, teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a "definitive manner," they propose in the exercise of the ordinary Magisterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful "are to adhere to it with religious assent"
422 which, though distinct from the assent of faith, is nonetheless an extension of it.
398 LG 19; cf. ⇒ Lk 6:13; ⇒ Jn 21:15-17.
399 LG 22; cf. ⇒ CIC, can. 330.
400 Cf. ⇒ Mt 16:18-19; ⇒ Jn 21:15-17.
401 LG 22 # 2.
402 LG 23.
403 LG 22; cf. CD 2,9.
404 LG 22; cf. ⇒ CIC, can 336.
405 ⇒ CIC, can. 337 # 1.
406 LG 22.
407 LG 22.
408 LG 23.
409 LG 23.
410 Cf. CD 3.
411 LG 23.
412 Cf. ⇒ Gal 2:10.
413 Cf. Apostolic Constitutions 34.
414 LG 23 # 3.
415 PO 4; cf. ⇒ Mk 16:15.
416 LG 25.
417 LG 12; cf. DV 10.
418 LG 25; cf. Vatican Council I: DS 3074.
419 DV 10 # 2.
420 LG 25 # 2.
421 Cf. LG 25.
422 LG 25.
Catechism of the Catholic Church - IntraText
(Continued in next thread)