Per my understanding, the implementation is same as 3-legged except you won't pass token and secret but empty strings. Client Application will need to have its client ID and secret stored in a secure mannercheck the flow- The OAuth Bible

You don't need to close the session here with service users using adaptTo()Remove this code..   if (adminSession != null){      adminSession.logout();     }

Are you able to login via /crx/de or /crx/explorer or /system/console/bundles using admin credentials?

You would run into issues where API contracts have been modified or deprecated even in case you reverse engineer the code. You'd need to have base project setup files (archetypes/library versions etc.) which are missing in this case.How would you even identify what library version is being used and ...

It still doesn't make sense to me. Couple of pointers if you wish to proceed:OOB code for http://localhost:4502/libs/cq/workflow/admin/console/content/instances.html​ is under  "/libs/cq/workflow/admin/console/components"For extending page properties checkEditing Page Properties Extending Page Prope...

Well, in that case, debug OOB code for the link you mentioned and find if you can utilize the same with a page path being passed to it dynamically.

That article was for reference, you won't find repo.xml in 6.4Configure the same in Day CQ WCM Version Manager and Purge Task available under /system/console/configMgrHow is this indexing issue related to version purging? You'd need to fix your index definition for that.

Wouldn't 'Timeline' feature suffice for this requirement? Within 'Timeline' you could choose 'workflow' or 'show all' based on your use case.

If /useradmin doesn't work, then there is another tool for more granular permissions -- /crx/de Create multiple groups and restrict the model paths for each group per your use case using this console. I would update this thread, if I get a better solution.

Limit  # page version creation, paths under which version can be created implicitly and age of versions. You could even choose to stop implicit version creation (after evaluating pros/cons) and move into manual mode that would be done by authors explicitly for specific project(s).That depends on you...