My point: truth is truth. It does not change. Popes cannot change truth.
It is just my opinion, but IMHO:
The truth does change and popes have changed the truth.
In the past a Pope taught that torture was allowed to extract confessions from heretics in the inquisition.
Presently, it is taught that torture is intrinsically evil and it is not allowed.
In the past it was taught that the Blood was shed for all.
Presently it is taught that the Blood was shed for many.
In the past it was taught that the Holy Spirit proceeds from the Father.
Presently it is taught that the Holy Spirit proceeds from the Father and from the Son.
In the past it was taught by the Church and by St. Paul that a woman must cover her head in church.
Today the truth is that women do not have to cover their heads in church.
In the past it was taught that marriage had two purposes: a primary and a secondary.
Today it is taught that the two purposes are equal.
In the past the truth was that it was a sin to charge interest on a loan. that is why this job was given over to the Jews.
Today it is taught that it is not a sin to charge reasonable interest on a loan.
In the past it was taught that capital punishment was admissable.
Today it is taught that capital punishment is inadmissable.
In the past it was taught that you make the sign of the cross from right to left.
Today it is taught that in the Roman rite you make the sign of the cross from left to right. (see the online Catholic encyclopedia on this point).
in the past it was taught that man can have more than one wife (e.g., Moses)
Presently, it is taught that man can have only one wife.