What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Unfortunately, required option is not available on form collapse. You can't make the form collapse required to work with the fields. In order not for the fields to be required under the 2nd collapse, just make the fields unrequired.
Or, you can also use "Require a form field" conditions depending on the user answer.
If you need further assistance on implementing this solution, let us know.