How can Acrobat Sign send both the initially sent and completed signed documents to a document repository??

We are evaluating an integration between Adobe Acrobat Sign and Hyland OnBase, which will remain our document repository and system of record.

For each agreement, we need to store two document versions in OnBase:

1. Document copy when the agreement is sent
   We need to store a copy of the document exactly as it was sent to the recipient. It will be This allows the business to verify later what document was sent and when it was sent.

2. Completed signed document
   After all required signatures are completed, we need to store the final signed document in OnBase

On the OnBase side, we have an existing Document Upload API that can receive the document and the metadata required for indexing and workflow routing.
 

Could someone please help clarify the following?

1. Does Acrobat Sign provide an event or webhook when an agreement is sent to the recipient?
2. At that point, can the exact document that was sent be retrieved through the Acrobat Sign API?
3. Does Acrobat Sign provide an event or webhook when the agreement is fully completed?
4. Can the final signed PDF be retrieved automatically through the Acrobat Sign API after completion?
5. Can Acrobat Sign call an external REST API, such as the OnBase Document Upload API, directly?
   If Acrobat Sign cannot call the OnBase API directly, would middleware or a separate integration service be required?
6. Is there an Adobe-recommended integration pattern, API example, or reference architecture for sending both the initially sent document and the completed signed document to an external document-management system?