Do I have to send all questions to the guest in one go or can I go back and forth? 

In our experience it can take some time for guests to respond, so going back to them a second time isn't always desirable. 

You can go back and forth, but generally you won’t want to wait for guests to submit their answers again, and some guests won’t want to take part repeatedly. 

It's more efficient to ask 'psuedo' follow-up questions up front, or interview multiple guests at once and combine their answers, to gain the richness sought. 

If you do want to go back and forth, here’s what you can do today:

Option 1) add a follow-up question in the same interview: your guest will see all the previous questions and all previously recorded answers and will only need to answer the new questions.

Option 2) create a new follow-up interview just for those 3 questions. It will be separate, but you can easily merge the audio from both interviews into Mix afterwards.

There is a feature request to better support back and forth: 

Our long-term solution to this is to implement A.I. follow-up questions in real-time