The simplest way to disable word-press updates by installing and activating Disable Updates Manager plugin from the given below link.
[https://wordpress.org/plugins/stops-core-theme-and-plugin-updates/][1]

WordPress updates disable by Manually

if you want to disable theme and plugin updates, then you can do so by adding below code in function.php file under Theme folder.

To Disable Theme Updates WP Version 3.0+

remove_action( 'load-update-core.php', 'wp_update_themes' );
add_filter( 'pre_site_transient_update_themes', create_function( '$a', "return null;" ) );
wp_clear_scheduled_hook( 'wp_update_themes' );

To Disable Plugin Updates WP Version 3.0+

remove_action( 'load-update-core.php', 'wp_update_plugins' );
add_filter( 'pre_site_transient_update_plugins', create_function( '$a', "return null;" ) );
wp_clear_scheduled_hook( 'wp_update_plugins' );

To Diasable Core Updates WP Version 3.0+

add_filter( 'pre_site_transient_update_core', create_function( '$a', "return null;" ) );
wp_clear_scheduled_hook( 'wp_version_check' );