Ask your questions in the comments below.
Does the Pope have authority to change doctrine or centuries-old liturgical discipline?
The Pope decides what is and is not correct doctrine. If a widely-accepted teaching is said to be a dogma, the Pope can decide that it is not a dogma, is not correct, and can teach the correct dogma in its place. So no one can oppose the Pope on the grounds that they have determined that an idea is dogma; the Pope can disagree, teach the contrary, and reject that alleged dogma. This is not the Pope changing doctrine or dogma, but teaching what is and is not truth. He has the authority over doctrine.
The Pope also has authority over discipline, and he absolutely can change disciplines that have been practiced for centuries. He it is who rules whether a discipline is changeable or not. If he rules it is changeable, then he may change it. No one can contradict him by claiming that a discipline is so old that it cannot be changed.