If I'm not mistaken, the First Vatican Council dealt with the theological issue of Purgatory.
The statement that the first one occurred in the 12th century is also inaccurate. Again, that only applies to Saros 129. The referenced page shows them going back into antiquity and forward as far as they've calculated.
What can I say? I'm an Astronomy Merit Badge counselor.
It did, but the duration of the stay is all hypothetical. There may be some folk tradition that speculates on that, but no doctrine. We don't know, for example, how long it takes to purge the aftereffects of a murder, or a broken fast. I would venture to say, we know that it is not knowable. This is one of those things that were a problem with indulgences.