1. Yes, there is, but it do not change the loading time of the game - if you disable the intro, you will be watching black screen until game load properly. To disable intro:
Enter the directory > My Document/My Games/Sid Meier's Civilization 5/ and there will be a document named UserSettings.ini. Open it. Find a line "SkipIntroVideo = 0" and change 0 to 1. Save the document. Intro is gone.
2. Nope. Resources are added to your empire as soon, as you make a proper improvement over them.
3. City States are extremly powerful add-on, that can make your empire spin! City-States are divided by two factors: type and, lets say, character. Type declares what kind of bonuses you can reap from it, if u are befriended with it or even better, allied with it. SO, cultural CS's grant you culture, militaristic give u new units once for a time and marinistic throw at you some extra food (only to capitol, if friend, and to all your cities if allied).
Character describes how fast your influence vaporize from the city (hostile CS's tend to forget your good deeds quicker x) ) and what time of "quests" a City State will want you to do to be your good fellow. Hostile, as you can guess, want everything killed, maimed and destroyed! Irrational is plain random - build a wonder, create a great merchant, destroy other CS's - you never know! And Friendly, will rarely want you to eliminate someone, but rather goes for "Build Pyramids to make us happy" or "Connect us with Yer'Ol Capitol". That stuff.
Generaly, bonus is bigger if you reach ALLY status with a City State. If you think this is not worth it, let me add that every CS that is allied to you give u access to its strategic/luxury rescources! That is big. Also, while allied with CS, and start a war, it will eagerly send its forces to fight for you. What not to love? WIth Patronage Policy Tree it becomes extra powerful, as it is way easier to handle CS's overaly and give additional bonuses, like increasing your science output, giving you Great Peoples and increasing happyness. Yes. Learn to love CS's
* However, it becomes less of importance on higher difficulities, as AI have more money to buy CS's at his wish.
* Also, try Patronage + Siam. Just plain crazy!