He was told it would be Elias, but the way he is described is NOT as the OT Elias, but rather a seemingly Holy Pope/Pontiff, and it doesn't mention how he comes to be, but IMO  canonical election by Cardinals doesn't seem to be the mechanism considering the deep rot/damage and satanic control that he prophesied would reign in Rome

Well, the Papacy had been in exile at Avignon for quite some time, and not a few prophecies refer to the Pope having to flee Rome ... and the reference you make is anachronistic and reversed, where Palmar sounded rather Palau-ian.  Since prophecy comes first by definition, anyone can try to pretend they meet the conditions, from Cardinal Spellman renting a boat with sheep in it to go up and down the Tiber, to lots of people claiming to be Enoch / Elias or the Great Monarch.  That doesn't meant the intial prophecy is wrong just because some nut-job later tried to conform to it.

Not to take anything away from good Fr Palau, but that begins to start a little Palmarian around the edges.

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This question has been discussed by theologians, and the most common opinion is that it is tied to the Faith that Rome will always exist, at least in a way that it will be able to have a bishop. The reason for this is that there are dogmatic definitions that say things like, "If anyone deny that someone must be submitted to the Roman Pontiff in order to be saved, let him be anathema." Or something along those lines.

The problem is that if there is no Rome, then the term "Roman Pontiff" has no meaning. Worse still, if the seat of the Church were moved from Rome to, let's say, New York, then that dogmatic definition would be null and void, because then one would have to submit to the "New York Pontiff" and not the "Roman Pontiff", and dogmatic definitions cannot ever cease to be true.

And how could the pope continue to be the Roman pontiff if the seat of the Church were moved to New York, and the pope was now the bishop of New York instead of Rome?

That's how they argue it.

But Roman is not synonymous with "Vatican City", Or "St. Peter's Basilica.
 
He is the "Roman Pontiff" because he is the Bishop of Rome (the diocese).

This seems obvious to me. Because the city itself can grow and shrink, and and take away church buildings, etc.

So in theory, as long as some of the city remained habitable it could qualify as still being a "diocese". Is that right? Or, are you stating the theologians argue that the Churches and buildings of the entity known as "Vatican City" that came about in 1929 should be equated with the whole diocese of Rome regardless of any extenuating circuмstances?

Get my drift? Thanks for the feedback.