B1/B2 visa for parents from India (HYD)

Hi, my parents and parents-in-law are appearing for their B1/B2 visa interview in Hyderabad consulate in a couple of weeks. I have couple of questions:

1. Would them appearing together on the same day during the time slot be a problem?

2. When asked “purpose of visit” - should they say “visit daughter and son-in-law” or just mentioning daughter be enough?

3. My parents along with my sister have applied together as a group. My sisters b1/b2 visa was rejected previously (2yrs back) under 214(b). Does her chances of approval increase now that she is appearing for the interview again with my parents or would my parents chance decrease because of my sisters previous rejection?

I’m kinda freaking out after hearing about all the rejections and experiences people have mentioned here especially at the Hyderabad consulate. So any words of advice or wisdom would be greatly appreciated. Thanks in advance!