www.example.com/wp-admin

example.com/wp-login.php?redirect_to=http%3A%2F%2Fsite.com%2Fwp-admin%2F&reauth=1

remove_action('template_redirect', 'redirect_canonical');

remove_filter('template_redirect', 'redirect_canonical');

add_action(
      'init',
      function() {
          remove_action('template_redirect', 'wp_redirect_admin_locations', 1000);
      }
  );

function custom_wp_redirect_admin_locations() {
global $wp_rewrite;
if ( ! ( is_404() && $wp_rewrite->using_permalinks() ) )
    return;
$admins = array(
    home_url( 'wp-admin', 'relative' ),
);
if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $admins ) ) {
           $wp_query->set_404();
           get_template_part( 404 );
           exit();
}
$logins = array(
    home_url( 'wp-login.php', 'relative' )
);
if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $logins ) ) {
             $wp_query->set_404();
             get_template_part( 404 );
             exit();
}
}

function remove_default_login_redirect() {
remove_action('template_redirect', 'wp_redirect_admin_locations', 1000);
add_action( 'template_redirect', 'custom_wp_redirect_admin_locations', 1000
);
}
add_action('init','remove_default_login_redirect');

add_action(
'template_redirect',
function() {
$requ = untrailingslashit($_SERVER['REQUEST_URI']);
if (site_url('wp-admin','relative') ===
untrailingslashit($_SERVER['REQUEST_URI'] )){
  remove_action( 'template_redirect', 'wp_redirect_admin_locations', 1000 );
}
}
);

function custom_wp_redirect_admin_locations() {
global $wp_rewrite;
if ( ! ( is_404() && $wp_rewrite->using_permalinks() ) )
    return;

$requested_url = untrailingslashit( $_SERVER['REQUEST_URI'] );

$admins = array(
    home_url( 'wp-admin', 'relative' ),
    home_url( 'dashboard', 'relative' ),
    home_url( 'admin', 'relative' ),
    site_url( 'dashboard', 'relative' ),
    site_url( 'admin', 'relative' ),
);
if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $admins ) ) {
redirect_canonical( $requested_url , false );
    exit;
}

$logins = array(
    home_url( 'wp-login.php', 'relative' )
);
if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $logins ) ) {
redirect_canonical( $requested_url , false );
    exit;
}
}

function remove_default_login_redirect() {
remove_action('template_redirect', 'wp_redirect_admin_locations', 1000);
add_action( 'template_redirect', 'custom_wp_redirect_admin_locations',
1000);
}

add_action('init','remove_default_login_redirect');

<?php
/**
 * @packageStop_Redirect
 */
/*
Plugin Name: Stop redirect
Plugin URI:
Description: Stop redirecting anything to wp-login
Author: Tomasz Struczyński
Version: 0.1
Author URI:
*/

add_action('init', 'remove_default_redirect');
add_filter('auth_redirect_scheme', 'stop_redirect', 9999);

function stop_redirect($scheme)
{
    if ( $user_id = wp_validate_auth_cookie( '',  $scheme) ) {
        return $scheme;
    }

    global $wp_query;
    $wp_query->set_404();
    get_template_part( 404 );
    exit();
}

function remove_default_redirect()
{
    remove_action('template_redirect', 'wp_redirect_admin_locations', 1000);
}