By their very nature, hidden fields will remain hidden no matter what. They can only be answered via the use of pre-filling or by setting a default answer.
What about if I want to show answers within a hidden field?
If you'd like to allow users to see data from Hidden fields, you can do so using answer piping with specific pricing plans. Hidden fields will also be present in your Submission Summary.
Gotchas
While the field itself will remain hidden, it's important to note that any answers passed via the URL can be seen and edited by the user.