question!

now that my username is changed, if I log in, can I still use my previous name to log in or this current username?

You log in with your current name. Because your name was changed, someone else can use your old name if they wanted/knew it.

It's better to activate the button that will never log you out whenever you refresh page or not been using era-go.
To make sure you don't forget any important identification.

Answered