We don't want same user to be logged in from multiple Systems. Can we restrict on number of instances the user logged in?
Take a look at this documentation, looks like you may have to enable transaction security policy
Note: As per docs to enable this feature
Requires purchasing Salesforce Shield or Salesforce Shield Event Monitoring add-on subscriptions.
This could be a better solution than the above mentioned route There is also this doc which provides solution using login flows