"If all this can change overnight, then what exactly is not subject to change?"
This might like a simplistic answer but here goes:
If you are Catholic, you are familiar with a prayer called “The Apostles Creed.”
If you study it you will see that it may be possible to change some things.
EXCEPT: EVERYTHING IN THAT PRAYER SAYS WHAT CATHOLICS BELIEVE.
ANYTHING THAT TRIES TO CHANGE ANY PART OF IT... A SENTENCE, TENET, BELIEF OR PHRASE...CANNOT BE DONE.
That’s what I believe.
Anything else is purely man-made rules and of little importance.
The Pope never is supposed to change any of it.
This pope, who is not Catholic, has his big nose into everything under the sun.
Hopefully that will change soon.