Hello @Giridharan Sivaraman ,
Thanks for reaching out.
As per the documentation, you can create todoTaskList for a user with user-id with application permission using the below endpoint:
POST /users/{id|userPrincipalName}/todo/lists
You can query all the users in your tenant using this endpoint GET
https://graph.microsoft.com/v1.0/users
where as the response contains id and that can be used to request the /users/{id|userPrincipalName}/todo/lists/{todoTaskListId}/tasks
endpoint.
Hope this helps.
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