Reserved for scenario information (There is no consolidated info on the internet, so I have to type word by word. You can read the scenario info in game. This is just for some quick overview)
Victory conditions: Highest score after 200 turns, where score can be earned by
1. Control or ally the holy city, or Jerusalem (10 points per turn)
2. Win election from civs and CSs on turn 50 and subsequently every 25 turns (250 points per election for the winner, no point if draw, maximum 1500 points)
3. Send caravels west after researching Exploration (500 points per caravel + gold, but each subsequent caravel drops in points, source: MadDjinn)
4. Capture cities following a different religion (25 per pop of the city before capture, ie. 10 pop before capture 250 points, source: MadDjinn)
Three religions are established before game: Catholicism (Vatican), Orthodoxy (Constantinople) and Islam (Mecca). The holy cities are predetermined and no great prophet is needed for that matter. Basically only Byzantium get hold of holy city in the beginning, so they will increase points by 10 each turn from the start. Other civs have to either ally or conquer vatican or mecca or Jerusalem to get that benefit (these 3 are city states, and has to be the same religion to get the founder belief).
Civs grouped by religions:
Isabella-Spain: after exploration, send 3 conquisitors to the west for addtional points according to 3, same UUs as G&K
Boudicca-Celts: 20% combat bonus fighting larger civilisation (Ethiopia UA), same UU + longbow like UU (similar to English UU I guess)
William-The Netherlands: same UA,UU,UI
Elizabeth-England: same UA, UU
Francis I - France: same UA, same musket UU + UB
Gustavus Adolphus- Sweden: NOT G&K UA, but actually repalced with Viking UA, the horse UU remains but with another UB
Maria Theresa - Austria: same UA, UU, but different UB.
Suleiman-Turks: all melee naval can capture ships. 1/3 naval maintenance, same UUs as G&K
Saladin-The Ayyubids (Songhai): free courthouse, start with The Pyramids, UU+UB
Ya'qub al-Mansur: The Almohads (Arab): +2 gold per trade route. Same UU, UB
Theodora-Byzantium: 1 extra spy, only civilisation starts with a controlled holy city, same UUs as G&K
Catherine -Russia: All land unit + 1 movement. Movement only cost 1 movement point along a river. same UU, UB
Units and upgrade path change
(Originally Posted by AriochIV)
A warning to those playing the scenario for the first time: Swordsmen don't cost Iron, but Longswordsmen do, and so do Musketmen and Cannon.
Frigates also require Iron, and the other ships do not, but this is normal to the regular game.
Also be aware that some of the upgrade paths are not available -- Triremes and Pikemen in particular can't be upgraded.
and Knights upgrade to Lancer/Cossack/Hussar/etc.
Some useful tips
Capitals and city states locations are predetermined before the game, so a little bit knowledge of European geography may help there, so you know who you will fight against early on based on historical locations.
Some first turn advice quoted from MadDjinn: choice has to be made very early in the first turn to whether going the Knight route or the Longswordman route, which can roughly determined if you can see horses or irons in the first a few turns. The HS has no free great prophet, so no one will go there.
For general intro as how to play each civ to the most advantage, please view the video above into several minutes.