21 questions is a game you play when you are on a dating web site and want to make yourself sound a lot better to the person you're trying to hook up with.
Hey, let's play 21 questions so I can lie about myself to you!
Any period of time where you and your friends go out without initial purpose or expectations. Usually in the early hours of the morning or late at night, side quests last as long as everyone is still out away from their home, dorm, or common meeting space. Side quests usually happen after a "main quest," scheduled hang out or party and usually feature less people than the original main quest.
"I'm bored but idk what to do... wanna just go out?"
"Hell yeah man let's go on a sidequest!"