Complex Survey Creation

My client has a 21-questions survey with the following components and needs for annual compliance training:

• Learners MUST give a response to each of the survey questions.
• Learners have the option to provide feedback on each question.
• There is one question that, if they select Other, they MUST put something in the required text field.

It's essential that users can't bypass this, and they regularly pull reports on these questions. In the last few years, this was done with Captivate (by another developer). I believe it would have to be multiple surveys as it is in Captivate; I cannot figure out how to do this in Storyline 360 with the survey, question, or freeform functions. 

I have attached a couple of screenshots of the current survey (including the one with "Other" as a choice and the required text field.) All suggestions are welcome!