For your first question, the Identity Now REST API provides two endpoints that you might find useful for obtaining information about access requests. list-account-activities can return information about access requests, and you can filter the results using query parameters to help you find the specific access request you need. access-request-status returns similar information. If you can’t find an appropriate filter to narrow down the results, then you’ll need to paginate through all of the results and use client side code to pick out the requests you need. Please see this post for more details on filtering access requests. Alternatively, you can use the search API to perform a search for access requests that meet your criteria. This might provide more useful results than the other two endpoints.
For your second question, I think you can you use the sources endpoints to get information about governance groups attached to the source. My IDN tenant is down so I can’t investigate this right now, but I’ll update this if I find a specific solution to getting governance groups for a source.
For your third question, I’m not sure what you mean by $plan attributes. Can you elaborate further?
And finally, if you want to track the status of access requests, please see my answer to your first question. The output of those endpoints can provide warnings, errors, and other data useful for debugging and tracking.