<?php
$post = get_post(6);
setup_postdata($post);
the_content();
wp_reset_postdata();
?>

function my_template_redirect(){
	if( is_404() && $_SERVER["REQUEST_URI"] != '/404/' ){
		wp_redirect( home_url( '/404/' ) );
		exit();
	}
}
add_action( 'template_redirect', 'my_template_redirect' );

function foo_theme_customize_register( WP_Customize_Manager $wp_customize ) {
    $wp_customize->selective_refresh->add_partial( 'blogdescription', array(
        'selector' => '.site-description',
        'container_inclusive' => false,
        'render_callback' => function() {
            bloginfo( 'description' );
        },
    ) );
}
add_action( 'customize_register', 'foo_theme_customize_register' );

add_action('customize_register', 'dco_customize_register');

function dco_customize_register($wp_customize) {
    //FOOTER
    $wp_customize->add_section('footer', array(
        'title' => 'Подвал',
        'priority' => 1,
    ));

    //footer text
    $setting_name = 'footer_text';
    $wp_customize->add_setting($setting_name, array(
        'default' => '',
        'sanitize_callback' => 'sanitize_textarea_field',
        'transport' => 'postMessage'
    ));

    $wp_customize->add_control($setting_name, array(
        'section' => 'footer',
        'type' => 'textarea',
        'label' => 'Текст в подвале',
    ));

    $wp_customize->selective_refresh->add_partial($setting_name, array(
        'selector' => '.footer-desc',
        'render_callback' => function() use ($setting_name) {
            return nl2br(get_theme_mod($setting_name));
        }
    ));
}

<div class="footer-desc"><?php echo nl2br(get_theme_mod('footer_text')); ?></div>