You've built a form and you've had workers submit forms against it. If you want to edit the form, say remove a question you will find that question delete button is disabled. This is because you cannot delete form questions with results against it. 

To remove form questions from a form, you will need to copy the form and archive the old one: 

1. Go to Forms Select Form and click Copy 

2. In the copied form you can now delete the form question and add in a new one. 

3. Tick the Publish box 

4. Click Save and Close 

5. Archive the old form 

We suggest that you start to use version numbers to keep track of updated forms i.e.
Pre-start V1
Pre-start V2