I can get it to do this too (v1.0.8)
turn on "Hide wp-admin"
turn on "Hide Login Page"
"Access error type" to 404
set "Set custom page 404 url" to "https ://google.com"
go to https: //your domain.com/wp-admin/
wp_safe_redirect will only redirect to a local url, not external to your site
when this redirect fails the original url is loaded again, hence a "to many redirects"
To enable external redirects line 211 of includes/classes/class.configurate-hide-login-page.php needs changing
from wp_safe_redirect($access_redirect_to);
to wp_redirect($access_redirect_to);