If you click on City Hall and choose nraas>sim, for whatever option you pick, a list of sims will appear along with their ages and portraits. You'd have to do some math, but for example on an unaltered normal lifespan, teens' ages range from 17 (on the day they age up from child) to 31 (on their YA birthdays). You can also use sim>focus and then pick "by age" and select "teen" if you want to see the entire town's population, although this will exclude true NPCs (for teens, all of the babysitters) who are not working and therefore are probably nowhere at the moment.
MC has two options to change a sim's age, Age: Absolute and Age: Relative; I believe both are under sim>intermediate (or possibly basic instead). With Absolute, you can set the age of the sim in question to one day short of her birthday, if you want; before you change the number, it will display how many days she has been a child, so you can also use this function to see when she would age up naturally. You can also just use MC to "trigger age transition," under sim>intermediate, if you're getting antsy.
As far as SP, there are a ton of settings you could customize, like Disallow Romantic for certain sims, but you should ask the experts (of which I am not one). There might also be something you can do to adjust how much time passes before another formal dance. You can use MC to force a sim to quit a job, or even dissolve a romance, if you don't like it. sim>intermediate>career and sim>intermediate>long-term relationship: by category, respectively; the latter lets you choose a second sim and then which category you want to assign to their relationship, like good friends instead of bf/gf.