how can i unlock my samsung GT-S5360 if i don't remember my gmail account and password

Question

how can i change my username and password for my gmail account

Answer 1

You can't change the username as that is the email address itself. You could create a new email account. You can use Googles normal account settings to change the password of an account and use their password recovery process if you have forgottenh it. No one else can help you.