How can I know the user id and information?

I've created a form and someone is using it in a wrong manner.
I'm getting prank registrations and the user is actually molesting the team.
Is there anyway through which I can get his/her information?

You can get the submitter's browser info by following this guide: https://www.jotform.com/help/234-How-to-Catch-User-s-Browser-Info 

And you can also get the IP address by following this guide: https://www.jotform.com/help/31-How-to-Find-IP-Addresses-of-Form-Submitters 

You could also set unique submissions on your form to avoid this person to submit the form multiple times: https://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form 

The get visitor location will also provide you with info about your submitter: https://widgets.jotform.com/widget/get_visitor_location 

Guide to add the widget to your form: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-your-Form 

Hope this helps.