Ludwig, yes to all 4. I always keep Culture above !00%. Chapter 2??
True you can have culture above 100%, that percentage represents the bonus growth of supplies and coins which is also dependant on the level of your residences and workshops. Now the actual available culture points you have could be less than what an upgrade requires. (ie/ numbers not exact, upgrade residence from level 3 to 4 requires 10 culture, your actual culture is 8 points, therefore you cannot upgrade until you get another 2 culture points) You can see how much culture you have available by hovering your mouse over the culture icon at the top of your screen.
Re: Chapter 2 - if you click the research button when at your city, scroll full to the left, in the upper left corner you will see a banner. It says " I The Arrival" Now scroll to the right until you see the next banner, it says " II Evolving". The block of tech researching in between these banners has been referred to as a chapter. Currently we have 7 chapters, the 7th being released just this week introducing Fairies and the technology they have to offer.