(2017, 2016, or 2015 edition) - The 60-Day GMAT Study Guide

Hello Together,

Request you to please let me know that having OG 2017 edition is sufficient or do I need to go for 2016 and 2015 edition as well .

Also while giving a diagnostic test and practicing questions do I have to attend the all the three 2017 ,2016 ,and 2015.

Regards
Rohit