Disable Wordperss Update to major 5.0 | Downgrade wordpress to 4.9.8

func.php

<?php
add_filter('pre_site_option_update_core','wpdg_specific_version' );
add_filter('site_transient_update_core','wpdg_specific_version' );
function wpdg_specific_version($updates){

	$sprache = get_locale().'/';
	if ($sprache == 'en_US/' OR $sprache == 'en'){
		$sprache = '';
	};
	$dg_version = '4.9.8';
	if ($dg_version < 1)
		return $updates;

	global $wp_version;
	// If current version is target version then stop
	if ( version_compare( $wp_version, $dg_version ) == 0 ) {
		return;
	}
	$updates->updates[0]->download = 'https://downloads.wordpress.org/release/'.$sprache.'wordpress-'.$dg_version.'.zip';
	$updates->updates[0]->packages->full = 'https://downloads.wordpress.org/release/'.$sprache.'wordpress-'.$dg_version.'.zip';
	$updates->updates[0]->packages->no_content = '';
	$updates->updates[0]->packages->new_bundled = '';
	$updates->updates[0]->current = $dg_version;

	return $updates;
}