Topic: F2A interveiw experience please !

HI first of all I am from Thailand, 17yrs My f2a case complete since April and NVC scheduled for me to interview at local us embassy on 16 this month at 08.30 am I am so worried can u guy tell me some experience for F2A minor child of LPR, Like the possible question they will ask and they request me to bring financial evidence include my dad i-864 and my co sponsor 864a with their tax return. Will RFE make it longer because it retrogresses on june. And should petitioner come with me on that day ? Thank and sorry for bad english.