1. I don't understand the concept of collateral damage. How does that work? It's not when the enemy attacks you, right?
2. How do I customize the game so it doesn't learn the most advanced techs at...say 1700 AD? (Keep the game from flying through the tech tree)
3. What is the lightning bolt on a city?
1. Various siege units, bomber units and battleships/missile cruisers do collateral damage when they attack another stack of units (not when bombing the defences of a city). This extra collateral damage is applied whether the siege units or battleship/missile cruiser wins the battle or not. Bombers have to get past the interceptors (ground based or fighters) to do their normal bombing damage and collateral bombing damage.
Collateral damage is applied to several units in the stack of units that is being attacked (5 to 8 units maximum depending on the type of siege unit that is being used and the number of units in the enemy stack). These units get an amount of damage which is half the amount of damage which is applied during a round of normal combat which means that it is usually close to 10 hitpoints of damage or about 10% damage (as units start with 100 hitpoints). Because wounded units are significantly weaker than full strength units, this means that these units can now be more easily beaten by other units. Attacking with units that do collateral damage can be especially useful in cases where the enemy stack of units has a significant advantage compared to your units as you can weaken several units at once and thus improve your chances of victory in the next battles. So when the enemy is hiding in a city or using defensive terrain bonuses or using a stack of mixed units, then you should be advised to weaken the enemy with siege units first.
2. The speed at which technologies are developed is very dependent on various starting game settings. A game on a pangea type map usually will have a faster tech rate because all of the civilisations have contact and can trade technologies and the foreign trade routes increase commerce output for everyone. A game at a high difficulty level will also experience a faster rate of technological development because the AI civilisations enjoy certain bonuses. And of course a game without technology trading will experience a slower rate of technological development.
If you want to play at the same settings and still want to enjoy a slower speed of technological development, then you could mod the game. The cost of the various technologies is stored in the file CIV4TechInfos.xml. A general cost modifier is stored in the file CIV4GameSpeedInfo.xml and in the file CIV4HandicapInfo.xml (note that the AI always uses the noble level modifiers and you'll use the modifier linked to the difficulty level that you're using).
Note that by modding these costs a lot, you could potentially make the AI less efficient in competing with the human player.
3. It's an indicator that shows that this city is supplied with power (which increased the production bonus of factories from 25% to 75%).
Ive always used it as a tool but now you got me thinking maybe it is actually preventing me from learning how to play the game because it keeps you from thinking about what to do next. hmmm
The AI doesn't know your plans and the AI controlling AI civilisations actually doesn't really plan things. You as a human being can do better than that.
You might plan to create a city which will produce a lot of units for you. You improved the terrain around this city to get a high production and you added military instructors that increase experience for units produced in that city. Still, the AI might suggest to build an observatory there which will not do a lot for your empire wide science output (because the city has a low commerce output) but will keep you from building units in this city. The AI just thinks 'Observatory will increase science output by 3 (example value). That's good.'
You might think that you need to get the currency technology quickly so that you can improve your economy (extra trade routes and markets) and expand your empire further without going bankrupt but the AI suggests that you invent horseback riding even though you don't have the horse resource.
The AI uses certain algorithms which guide its choices, but these algorithms are just based on the situation in that turn and aren't nearly as sophisticated as the planning of an average human player.