I'm in a similar situation, I'm in US and need to apply visitor visa for my parents. Will be glad if anyone can answer my questions:
1. Does both the parents attend the interview together?
2. And can any one of them answer all the questions asked by VO?
3. And do we choose a different language interview when setting up the interview appointment?
1. Yes, very much possible. Just request for this once they go for appointment.
2. If it is a pointed question to one person, same person must answer, else it goes against them. If the question is for both, either may answer, however, both must answer a few questions, it should not be that just one person has answered all such queries.
3. Surely. Many languages are available. It may affect your visa appointment date, as all languages are not available every day.
FYI, these things are very weird. I was not asked a single question. Guy just took my passport and put it in the slot and said "your application has been processed, you will receive your passport in 2 days time". Considering my passport has stamps of all war torn countries in middle east, it was a minor feat in itself.