Opening night is open to the public. Given that it's not the Broadway opening night, it's not going to be as "fancy," aka, it isn't going to have a dress code beyond that of the theatre's unless it was communicated to you at the time of purchase or if they send out some type of notice. If you're worried, contact the National and ask.
As for stage door - no one's going to know their intentions. If they don't stage door that night, you could always go back the next night (if that's an option for you).
Updated On: 10/22/13 at 02:16 PM