I want to link my other main account to my gmail, but unfortunately my gmail is already connected an existing account that I made in the past, so how do i permanently delete that account so i can link my gmail to my present game account?

You cannot, once attached always attached.

@victor-mellomida not possible . . . For that you need another e-mail or fb account. Once an account is linked, there's no going back

If i'm using mobile app, can i change my name or profile?

@benjosephlie the in-game name you can change it once if you haven't done it previously, for the pfp you can change it as many times as you want for the ones available in there