How to get Custom Taxonomy ID from the post ID

You can use wp_get_post_terms() which will return all the terms attached to the post, if any. Then, the first term of the array will be able to tell you which taxonomy it belongs to:

global $post;

$terms = wp_get_post_terms( $post->ID, array( 'regions', 'sections' ) );

if( ! empty( $terms ) && ! is_wp_error( $terms ) ) {
    $taxonomy = $terms[0]->taxonomy;
}

I do not know what your taxonomy slugs are so I guess, you may need to change them to fit your specific setup.