EDIT: This is answering the question about age:
In my opinion Rarity is probably the oldest, and Pinkie is probably the youngest. Pinkie still lives with her adopted parents (I always thought they adopted her because in the flashback she had the rock farmer parents, who looked totally different.) And Rarity runs her own business. Twilight is some sort of a student or intern, so she can't be too old, Fluttershy doesn't have a job, more just takes care of critters, I have no idea how old she is, Rainbow Dash is the same thing, no job, and Applejack still lives with the Apple Family but they always live together, Big Macintosh lives there but he's obviously older. She does family chore like things to help the business, she's probably a little on the older side. I don't know for sure.
I'm having a terrible day. Good god, I have braces (Don't think of me as too young, everyone says it's weird for someone this old to have braces, I'm years after the usual brace period, but anyway) and they got tightened yesterday morning. It's now been 24 hours and they still hurt like crap... I don't think it hurt this much when I got them on.