Civilization – Does the AI have a mechanism to know somebody engineered a war against it

This page has a number of interesting tidbits that aren't easily discoverable, including the one you mentioned above about Greece. Nothing else about civ leader specific abilities though.

You can skip the intro movie by hitting Escape; however, the game loads data in the background while the movie is playing, and therefore the movie won't actually stop until background loading is complete.

To access predefined maps, such as the Mesopotamia map that was part of some special editions, choose Mods and then Single Player. You can now select among all installed maps by clicking on the map button.

To show the movement range of a selected unit and the path it would take when ordered to move, either press "M" or hold down the right mouse button while moving the mouse cursor over the map.

The maximum radius within which a city can allocate workers is three hexagons in any direction.

Marble speeds production of all wonders by 25% in the city that works the quarry.

Greece has the special ability that moving units through the territory of city states never degrades influence with them.

Railroads not only give the usual gold & movement bonuses for roads, but also +50% production for cities connected to the capital. Harbors act as railroad connections as soon as the technology is available. The exact movement bonuses for roads & railroads are unknown.

Units count towards a supply limit defined by your cities and population, shown on the military overview. The exact effect of reaching that limit is unknown.

Units have a maintenance cost (aka upkeep) in gold which depends on your total number of units, and is summarized in the economic overview. The actual formula for unit maintenance is as yet unknown, and may or may not be related to the unit supply limit.

If you have no gold left and are running a deficit in excess of 5 GP per turn, units will begin to be forcibly disbanded to save on maintenance costs.

Razing a city takes one turn per population point, and begins only after you end your turn. So if you choose to raze a conquered city, you can still enter the city screen and cancel the razing. The city will then be annexed -- you cannot turn it into a puppet state anymore.

Pacts of Cooperation make the AI friendlier and more receptive to other deals. Pacts of Secrecy against another player do the same but with the added condition that neither player must cooperate with the target player.

Being allied with a city state grants you an automatic view of all tiles they can see. There is no other form of map trading; the only way to explore a major civilization's territory is to sign Open Borders and scout it with your units.

The manual once mentions that hotkeys are documented in the readme file, but they are actually listed in the manual itself on page 207. You should still have a look at the readme file ("Read Me .pdf" in your Civ5 installation folder) as it has some other useful information, such as the location of the editable Civ5 initialization file.

Looking for the real-time clock? Remember this is a Steam game -- if you have the misleadingly named "Steam Community In-Game" enabled in your Steam settings, you can simply hit Shift+Tab and get a big fat clock in the top-left corner, along with other Steam UI.

Here is a list of all the effects from happiness level that I could find. To answer your specific question, most of the effects care only if your civilization is happy or unhappy, by one :) or :(. (I believe zero :) is fine.) But there are three effects that care about the amount your civilization is happy or unhappy:

• VERY unhappy occurs when you hit -10 happiness. (Thank you @Oak)
• Golden Age points accumulate (or deplete) equal to the amount your civilization is happy (or unhappy)
• Piety->Mandate of Heaven uses your exact excess happyness to calculate how much culture you get.

Full list of effects:

Happy

• Growth: Cities grow normally.
• Golden Ages: If you have excess happiness, each turn it accumulates into Golden Age points, and when you have enough, your civilization enters a Golden Age. After the golden age the process starts again, although I believe you need more Golden Age points for each subsequent Golden Age.

Unhappy

• Growth: Cities grow at 1/4 speed when your population is unhappy.
• Golden Ages: The amout your civilization is unhappy is subtracted from the Golden Age points.

VERY unhappy

• Growth: Cities do not grow.
• Units: Settlers may not be trained.
• Production: Cities generate -50% production.
• Unit are less effective in combat. They get -33% combat strength.

VERY VERY unhappy (-20 or lower)

• Rebels will spawn in your border and attack your city

Social Policies

• Piety->Mandate of Heaven allows you to add 50% of your excess happiness to your culture each turn.
• Rationalism->Sovereignty boosts science +15% when your empire is happy.
• There are numerous social policies that affect the happiness level, but these are the ones that get effect from the happiness level.

Sources:

• General info: mousing over the happiness listing on the top bar, left side, during various happy states.
• Golden age info: mousing over the golden age display on the top bar, left side, during various happy states.
• Combat info: Comparing happy (normal) combat strength to VERY unhappy combat strength, by mousing over an enemy unit. The VERY unhappy combat modifier is clearly listed in the calculations.
• Production info: mousing over a city's production listing in the top left when VERY unhappy.
• Social Policy info: The social policy screen, accessible by clicking on the culture listing on the top bar, left side.