👋 @himankgupta81, I have an update! 😸

2- Is there any time lag between the activity performed and the last active date updated in the report? If yes, then how much?

I spoke with one of my colleagues and they shared their input with me:

When a GitHub Enterprise Server site administrator requests the All Users Stafftools report, a background job is started to generate the report based on information contained in the GitHub Enterprise Server database. Once the background job completes the report is available for download. The time it takes for the Stafftools report background job to run may vary depending on the current load and performance of your GitHub Enterprise Server, although on non-busy instances we’d usually expect the job to completed within several minutes.

For a performant GitHub Enterprise Server instance, there shouldn’t be any delay between actions the user performs and the user’s last_active date as reflected in the Stafftools reports.

You also asked:

3- Which all activities qualify for updating the last activity date of the user?

Here’s a list of actions that will update the last_active field:

• active sessions: An active session is a day that the person has visited the site while logged in. Excludes people who have visited the same day they signed up.
• web edits: A web edit is using the web UI to create a branch, tag, or do a file
  create, edit, delete operation.
• pull requests: Submitting a new pull request
• issues: Submitting a new issue.
• comments: Commenting on an a Commit, an Issue, a Pull Request, and Pull Request Review Comments.
• pushes: Git Pushes.
• wiki edits: Creating, editing, and deleting a wiki page.
• releases: Creating a new Release

We hope this helps!