Well I figured it out myself. I just did a simple trick. I reset the plugin and deleted it. And downloaded a copy of it in the computer, extracted it. Opened the pie-register.php and piewpnun.php on notepad++ renamed all the “pie_veification” and wp-login” with find button. Then I again installed it and before activating it just replaced those files in pie-register plugin folder with my edited files. Which did my purpose. Thank God.
