Hi,
Question - 1 : How to find the SAP user last login details
Answer : Please use SUIM transaction to check the last logon details of the user. Please check here SUIM-Overview and uses
Question - 2 : How to find who have added the Tcode in the Role.
Answer : Add the transaction code under menu tab the role which will add required authorization objects in the role. you have to adjust the objects (e.g; full access or restrict the access in the objects), save and generate the profile
Hope this helps.
Regards,
Pradeep