(I remember narrowing it down to ninth century Ukraine, specifically something to do with one Pereyaslav, but after that I guess we lost interest)
Ukraine - yes.
Pereyaslav - ???
the Fifty Years War (collapse of the British Empire FTW?)
Even I can't remember all the intricate details right now, though I probably have them written down somewhere. Anyway, the gist was that, after a period of relative modernisation (through forceful, rushed means) and military build-up, the French theocracy went all-out against Flanders and Britain, both of which were weakened and distracted by their own wars (in which the HRE supported Flanders). Having built up an impressive fleet, the French actually managed to achieve naval supremacy, while their massive armies succeeded in overrunning most of Flanders and Britain, while bleeding the Imperials white in border wars. Ultimately their gains proved untenable, but for the duration of the war the French had made sure to make as big a mess of the occupied territories as possible, inciting ethnic and religious strife, granting independence to puppet governments in separatist regions, destroying infrastructure, relocating manufactures and so forth. Ultimately the French retreated, but due to the sheer exhaustion of their enemies - who oftentimes also had other problems arising elsewhere - managed to avoid being defeated conclusively and even annexed the small Spanish state of Leon.
the "significant butterfly effect" that forced the French to move their capital
Now
that I definitely don't remember, but really, it could've been anything; France was, though this is hard to believe, even more belligerent than in OTL, and during or after any foreign invasion or civil war the capital might've moved to what was judged a more secure location. Then again, the theocracy's power-struggles with the traditional nobility and the bourgoise of Paris might've motivated them instead; that's probably more likely, especially given the influence of the Archbishops of Tours, a title often combined with that of Cardinal of France (i.e. effective leader of the French Catholic Church).
the reason for Crusader States in the Indian Ocean
After the conquest of Egypt, Venetians used Crusaders to secure valuable positions in India. They didn't hold on to all of them, but the Knights of Ceylon survived even the collapse of the Venetian colonial empire in the late 17th century.
how exactly Balkan politics worked for a millennium,
For most of the time it all rotated around Hungary, at least after the Early Middle Ages during which the Polanians were obviously of greater importance thanks to their conquest of Constantinople (and other places). When Hungary was strong, it more or less conquered the greater part of the Balkans (sometimes it contented itself with overwhelming political influence on local petty rulers, sometimes it really went, conquered and annexed what it could); when it was weak, it fell back, and Serbs or Bulgarians or occasional Greeks or Macedonians achieved limited local hegemony, though mostly it was just constant petty warfare and state-building.
In the 17th century, things changed; the Imperials began to take interest in the Balkans after establishing a friendly dynasty in Hungary, and more importantly, the Egyptians conquered most of the land south of Danube under their great King-and-Emperor Alexander I in a prelude to the Alexandrine War in Italy. After Alexander's eventual death, the Egyptian hold on the gains in Europe evaporated quickly enough, but even though the Hungarians reclaimed northern Balkans the Egyptians held on to Greece for long enough. Still, in the end, a loose Hungarian hegemony was imposed and was maintained with varying success for much of the 18th century.
In the 19th century, with the rise of nationalism and a renewed antagonism between Hungary and the HRE, that came crashing down amidst rebellions thanks largely to the Imperials. After losing most of the Balkans to rebels and being thwarted in their efforts to reassert control peacefully by a forceful Serbian monarch, the Hungarians made one last bid for power - the Third Balkan War. Despite some initial successes it turned out to be a catastrophe unparalleled after the Imperials entered the war on the Serbian side and utterly crushed Hungary, while the Serbs still managed to successfully play the "common enemy" card, amongst other things, to peacefully integrate most of the Bulgarian Principalities. Deciding that friendly and unified Balkans were definitely a good thing now that Chernigov was awakening and Hungary was revanchist, the Imperials helped the Serbs re-unite the Balkans, even turning the blind eye to their claiming of the Romanoi imperial title. Although somewhat tenuous for obvious reasons, the Serbo-Roman state has thus far been quite successful in most regards.
if he's going to write up a summary after the exams/after AFSNES' IT is over.
Really not sure.
too bad they never existed.
