No, you can't edit it, and that's a Meta rule, not an Ads Editor limitation. A published instant form can't be changed, otherwise old and new leads would end up in different formats in the same database.

The way around it is to duplicate the form and adjust the copy, and you can do that inside Ads Editor:

  1. Open Edit ad and go to the Lead Form section.
  2. Select the form you want to use as a base from the list.
  3. Click Duplicate form.
  4. Name the copy (by default it's "original name (copy)").
  5. Confirm. The copy keeps the same questions, privacy policy, thank-you screen and context card as the original.
  6. The copy is selected automatically. Click Save to apply it to the ad.

To change the copy's questions, use Meta's Instant Forms Library (the View forms in Meta link, in the same section), as long as the copy hasn't received leads yet.