What was their purpose in The Shawshank Redemption and lesson(s) learned from: Warden Norton, Brooks, Andy Dufresne, and Red?

The Shawshank Redemption
(1994) has become one of America's most acclaimed films
despite its weak showing upon release. Nominated for seven Academy Awards, it was
overshadowed by the year's two most popular films: Forrest Gump and
Pulp Fiction. 

ANDY
DUFRESNE.  The film's protagonist, Andy is wrongly convicted of a double
murder and given two life sentences. His intelligence and inner strength help him to
deal with his dilemma, and his ultimate escape reveals that he has spent several decades
slowly creating a tunnel that will provide his exit. He portrays a man who never gives
up and, despite his assistance in Warden Brooks' fraud schemes, eventually gains justice
when he turns over records that will condemn the warden. His dream of living out his
life on a beach in Mexico eventually comes true, thanks to his determined resolve to
maintain a humane civility under the trying circumstances of prison
life.

WARDEN NORTON.  Norton
is the Bible-thumping prison revisionist and primary antagonist of the film. Norton's
apparent do-good character is a cover for the illegal kickbacks he receives for
providing cheap prisoner labor. Amidst the murderers that fill the prison he
administers, he is just as evil as his prisoners: He orders a murder and deliberately
hides evidence that may free the innocent Dufresne. He serves as a reminder that some
men eventually get their just reward; when officials come to arrest him, he commits
suicide instead.  

BROOKS. 
Brooks is the old lifer, a kindly man who loves books. He is eventually released but is
unable to adjust to the life of a free man; he eventually commits suicide, hanging
himself from the rafters of his rented room. He is a tragic character, liked and
respected by all the prisoners, but an outcast in the outside
world. 

"RED"
REDDING.  Red becomes Andy's best friend, a sly businessman
inside the prison walls who, like Brooks, cannot adjust to life outside prison when he
is finally released. Contemplating suicide himself, he decides to visit Andy's secret
spot in Buxton. There he finds the money that enables him to join Andy in Mexico, where,
hopefully, the two friends live life happily everafter. Red serves as a character who is
able to adjust to prison life and even make things livable and profitable. As the
narrator, he serves as the conscience of the film: a noble character who, despite his
flawed past, will not make the same mistakes if given a second
chance.