17 minutes ago, Razi said:no using only change this simple line its not possible to reinstall complete classic theme.
if you have files and database access then you are able to edit the database table "employee" and add your new user password.
Hi,
I didn't need to reinstall classic theme. I just needed to activate it. And activating debug mode helped as well.
Admin page didn't load at all - blank page, I didn't loose password.
I did solve it, but thanks anyway.