Updating a question on a page
Any question can be edited in the page builder.
To do this:
In the preview of the page, click on the question to be edited.
The question will become highlighted, and the settings pane will open on the left hand side, populated with this question's settings.
Edit as necessary.
Click Update Question. The settings pane will close, and the preview will update to reflect the changes to the question.
Changes made to live forms affect data export
Changes made to the form structure can affect data exports. See Data Export: Changing Form Structure.