There is no such thing. Each pope has his own Magisterium. It just means Official body of work. They self regulate as far as not clearly disagreeing, usually by not stressing that there has been any change. For example, the last few popes have said they believe in Darwin, but have not in doing so called out the anti-Modernists as wrong. If they really wanted to be helpful, they would promote theologians who have laid out an alternative vision of original sin that uses Adam and Eve as mythical characters and the myth as illustrating blame rather than disobedience, although because of the Monsigor in question, writing about such things has been surpressed, much to the deteriment of the faithful. I know your brand wants pat answers, which is an aspect of loyalty. Faith is doing the right thing without them.