samsung s6 edge plus unrooting help needed

Hello,
My phone is 5.1.1

Q1 . Which firmware will work for unrooting from website below?
http://www.sammobile.com/firmwares/database/SM-G928T/

Q2. How to unroot phone SG928T to stock firmware? Will this guide work for s6 edge plus?
http://www.androidrootz.com/2015/05/...d-s6-edge.html

Thank you