Aria
What does “mean it” mean? And can I replace that expression with “for real”, “really”?

In this context, "did you mean it?" has the same meaning is "are you serious?" or "are you telling the truth?" It holds a bit of a different meaning than "for real" or "really," but the effect is similar. Ex. Then everything that you said before - did you mean it? Ex. I'm sorry, I didn't mean it.