Hi Abhi,
Go to SE80
Go to Package GRAC_ACCESS_REQUEST -> Web Dynpro -> Web Dynpro Application -> GRAC_UIBB_END_USER_LOGIN
Open the webdynpro in Admin mode and then right click on the page and you can Edit whatever text you want in End User Logon page as well as can enable and disable fields according to your requirement.
Regards,
Madhu