Non Logged in Users Error Message and Kill Previous user if already present
System rule has been configured to allow only one operator. When already logged in operator logins again then the error message is being displayed in next screen, but we need the error messaged to be displayed on the login screen itself and also an option to kill the previous user.
A similar function can be observed if you start performing a flow action on a case in one requester, and then attempt to perform a flow action on the same case from another requestor logged in as the same user. The ootb behavior is to put up a screen telling you that another requestor already has the work locked, and giving you the option of killing that other requestor so the lock will be released. Although this isn't exactly what you describe, if you use the Pega tracer to trace this ootb behavior, you can see how it is implemented, and base your design similarly.
This is an expected behaviour for when there are Number of concurrent sessions allowed for each operator exceeded. For example the value is 2 then it will allow 2 times for operator and while attempting third time it won't decide/display which one need to kill.
Agree but the business requirement is to show the error message on the login page itself and an option to Kill the Previous one. We have configured only one session per operator so there is no confusion on which session to be killed as there will be only one previous session.