How can I amend a form question without losing the previously submitted answers?

How can I amend a form question without losing the previously submitted answers?

The best approach for this would be for you to backup the submission data before you change the field as when you change the field(delete) the data will be deleted too.

https://www.jotform.com/help/44-How-to-Export-Form-Data-to-Excel

https://www.jotform.com/help/73-How-to-Download-Form-Submissions-as-Excel-CSV-PDF

Kindly do let us know if you ned further assistance.