Wordpress Two Step Login

Wordpress Two Step Login

I would like wp login form to have two steps authentication.
1.) If the username exists, ¹ password field appears.
2.) If the username doesn't exist, the password field is hidden.

¹ visitor must type correct username to proceed to step two.*

Where can I begin my quest to have the login form "detect usernames" in
the DB?
If there is a better way, may you please share your idea?

Thanks for your attention,