Enabling Back button and default username for logging in

[apothem]

How do I enable the Back button on my keyboard so that when I press it on my browser, I will go to my previous page?

Also how do I make it so that when my laptop boots up, only my password is needed? So for example, I start up my laptop and it will say "Apothem" and below it "Password: ", and all I need to do is enter my password to just log in?