Dear Ilia,
Thank you for your query and for raising it here in the public discussion forum.
I think you should be using the Forge BIM360 REST API to access models on BIM360:
https://forge.autodesk.com/developer/documentation
Here is a tutorial showing how to download files from BIM 360 document management:
https://forge.autodesk.com/en/docs/bim360/v1/tutorials/documen-management/download-document
This question and similar related issues have been discussed previously here in the forum.
One of the more extensive threads presents a couple of suggestions:
https://forums.autodesk.com/t5/revit-api-forum/browsing-model-files-in-the-cloud-a360-c4r/m-p/843279...
In it, Ali Talebi says:
This can be used to open C4R models directly via the Revit API where it was not possible via Forge. I think the Forge API can already help with the BIM360 part.
I hope this helps.
Meanwhile I have asked the development team whether they have any more up-to-date suggestions for you.
Best regards,
Jeremy