Put this codes on functions.php

Optimization WordPress Sites

/**
 * Disable the emoji's
 */
 function disable_emojis() {
  remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
  remove_action( 'wp_print_styles', 'print_emoji_styles' );
  remove_action( 'admin_print_styles', 'print_emoji_styles' ); 
  remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
  remove_filter( 'comment_text_rss', 'wp_staticize_emoji' ); 
  remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );
  add_filter( 'tiny_mce_plugins', 'disable_emojis_tinymce' );
 // add_filter( 'wp_resource_hints', 'disable_emojis_remove_dns_prefetch', 10, 2 );
 }
 add_action( 'init', 'disable_emojis' );

//hide wp xml-rpc
add_filter('xmlrpc_enabled', '__return_false');

//disable json rest api
add_filter('json_enabled', '__return_false');
add_filter('json_jsonp_enabled', '__return_false');

// disable rss feed
function wpb_disable_feed() {
wp_die( __('No feed available,please visit our <a href="'. get_bloginfo('url') .'">homepage</a>!') );
}
 
add_action('do_feed', 'wpb_disable_feed', 1);
add_action('do_feed_rdf', 'wpb_disable_feed', 1);
add_action('do_feed_rss', 'wpb_disable_feed', 1);
add_action('do_feed_rss2', 'wpb_disable_feed', 1);
add_action('do_feed_atom', 'wpb_disable_feed', 1);
add_action('do_feed_rss2_comments', 'wpb_disable_feed', 1);
add_action('do_feed_atom_comments', 'wpb_disable_feed', 1);

// remove the header links to your RSS feeds.
remove_action( 'wp_head', 'feed_links_extra', 3 );
remove_action( 'wp_head', 'feed_links', 2 );