Councils are until changed. Popes too. Infallibility is more a discipline than a promise, which leads to some interesting logical gymnastics when change is necessary. Trent had changed lots of practice and their condemnations of Protestantism are hollow as they protest the superiority of Constantinople (Peter). Example: The Mass had multiple prayers to St. Michael. These are now absent from the Roman Missal. Pius called his Mass unreformable. It wasn't.