I'm [still] searching illustrator for enough parity to switch from InDesign. Can I change the swatch color and had everything with that color over 100 art boards all change? We'll see... Can I change the padding around text areas from 12px to 16px project wide? all that stuff...
Your latest questions are way off the original question asked four years ago, and on a different application so they merit their own thread on the Illustrator forum. I'll branch it over there now.
And to address the first new question. Yes, Illustrator supports global colors. If you edit the definition, Illustrator updates all of the objects that are using that color.
I don't do web design work in Illustrator, so I can't address the second question.