Can a Pope be impeached?
No. He’s there for as long as he lives.
Not all popes live as long as others.
No, but he could always be declared an Antipope and a rival can be put up in his place.
Of course, that hasn’t happened in a loooong time.
I hope not, for then Vice Pope Biden will be elevated.
Not impeached as such. But it is the opinion of many saints and theologians that if the Pope were ever to become a manifest heretic, he would lose the office immediately and the see would be vacant. Then there would be another election.
Now how that determination of heresy would be made in real life, I don’t know, as I don’t believe there is precedent for it, but that is one mechanism for dealing with problems in this regard.