Immediately after, actually, because it was the succession custom in the County of Barcelona (whose house was now the kings of Aragon). But when it was necessary to challenge the succession it went back to the original Aragonese laws, like with Ferdinand I, that you mentioned. In the Compromise...
The reason Barcelona was part of Aragon was that the count of Barcelona, Ramon Berenguer IV, married the heiress, and later queen, of Aragon, Petronila I, who inherited the throne from her father.
If they go this direction, and given the Ottomans are their nemesis at this time of history, they may be very tempted to go the way of the Roman Empire and try to conquer Egypt to become the imperial breadbasket.
All of those languages were once fully developed national languages. What will probably happen is that the common standard will be a mix of castillian and portuguese, and those two languages will slowly disappear until they are only found in rural areas.
Indeed. The Spanish Hapsburgs were very active, but the reason there were spanish hapsburgs in the first place was because the Catholic Kings created a net of marriage alliances with their children, and then the heir died.
France became the enemy to beat for Spain as soon as they had the Reconquista business over. They are neighbors, they had conflicting interests in Italy, and they had claims in each other's border areas (Navarre and the Rousillon). They became dragged into European (read: HRE) conflict due to...
"Significantly" may mean it went worse, too. Let's not pretend that early 20th century Australians were less dismisive than their british counterparts about people they considered lesser.
Columbus was Genovese, but Gil Eames, Bartolomeu Dias and Vasco da Gama were all portuguese. The Iberians had plenty of experience with atlantic navigation, and the Italian naval involvement was a cause for that, not a impediment. Because the Italians controlled the Mediterranean, Castille and...
We are already at the end of the 15th century. America should be discovered any decade now, and even if they are not conquered as OTL the silver will reach Europe via trade. The conditions for the discovery aren't much changed: Western Europe is cut off from the path east to Asia; the fact that...
Or it could go weird. I do remember the background fluff of some timeline (now that I think on it, it may have been one of GURPS alternate worlds, it was a long time ago) where the Papal states survives, but one of the popes took the whole "give Caesar what belongs to Caesar" rather seriously...
It seems he at least survives long enough to return his diary to the ducal archives, and the fact that it is kept in the dual archives in the first place is probably a hint that he lives long enough to become important for Venice somehow.