That's an understatement.
Even if many of her officials are given over to sin for a season, her doctrine remains pure.
No, it doesn't. It's been revised more than once. The Council of Trent was one time and Vatican II another.
The Council of Trent did not revise but confirmed existing doctrine. Vatican II began with Pope John XXIII promising no change in doctrine. Even though the council employed vague, feel-good, Sixties language, no doctrines were actually changed.