Disable WordPress Auto Update ( No Plugins )

Add this code in function.php file

// Disable Autoupdate
add_filter( 'automatic_updater_disabled', '__return_true' );

function remove_core_updates(){
global $wp_version;return(object) array('last_checked'=> time(),'version_checked'=> $wp_version,);
}

add_filter('pre_site_transient_update_core','remove_core_updates');
add_filter('pre_site_transient_update_plugins','remove_core_updates');
add_filter('pre_site_transient_update_themes','remove_core_updates');