How to change my user name Vaisakh v to vaisakh vijayan
From Google help Edit your Google Account information
You can edit information like your name, birthday, gender, and the email and phone number associated with your account. This basic information is used to help others get in touch with you more easily in products like Hangouts, Gmail, and Maps.
Sign in to My Account.
In the "Personal info & privacy" section, select Your personal info.
Choose the information you want to edit and follow the onscreen instructions.