God is constant, Pope?

I am not a catholic but I know about the catholic denomination from friends and acquaintances and from study on it. There's an awful lot of news on it since the pope just died, and I am learning more because of this.

One of the questions asked is who will the new pope be and will he carry on as John Paul II or will he go a different way.

Here's my question/thought. Example-God in the Bible tells us premarital sex is wrong and will cause hurt/confusion with a person's emotions. God is constant on this fact.

If the next pope comes in and declares that premarital sex is OK, he can do that, right? Because he is considered infallible, he knows and can interpret things through his "view". I know Pope John Paul II declared that God used evolution in creation(this is not Biblical), so it was then acceptable for a catholic to believe this. It had ripple effects with others also.

I used premarital sex as an example only. There are many many other things he can declare to be new truth, right?

The Pope can’t make fundamental changes in the church like that. Their laws and so forth are all based on scripture not the whims of a Pope. Certainly their interpretation of scripture can play a part on the Popes stance but such a basic law like no premarital sex and the like can never be changed.

I hope I am naming these meetings right. There was a Vatican 1 and Vatican 2 that deals with interpretaion of scripture and involves cardinals. And they do reinterpret things at these meetings, don't they?

I hope I get all this right. It's been a long long time.

Dogma, Doctrine, and Discipline.

Dogma = revealed truth
Doctrine = Teachings drawn from doctrine to contend with specific conditions and situations of Christian living.
Discipline = Church law -- deals with matters that are not neccesarily of Dogma or Doctrine.

Of the three only Dogma cannot be changed. Dogma must be accepted. period.

One of the dogmas of the Catholic Church is the papal infallibility. The pope is infallible only when he speaks ex cathedra (a specific type of papal decree) a doctrine of morals or faith for all the chruch.

If a doctrine is made ex cathedra it is effectively unchangable. If it is not, it is possible to change it.