Approval workflow: editing previous submissions

I typed up my question and it did not save on submission, so I am retyping it on edit.

We have a form (AAO Convo 21 CME Attestation) that we are using to verify course completion. We would like to take advantage of the approval workflows to review and approve the forms, then send email notice of approval with an attached PDF certificate of participation.

We have already received several submissions, but would like to try to implement this process on new and existing submissions.

I have created the PDF certificates, but am having trouble setting up the approvals and understanding how the approval workflow will affect previous submissions.

What is the best way to implement this process on an existing form with submissions?

Will the process work if approvals of submissions are edited on the backend? Or does the approver have to receive the email with the link to edit in order to approve?

It is not possible to trigger approval flow for the existing submissions by editing submissions, but you can start the approval flow from Inbox.