You are using all three of these functions incorrectly. Please always check the documentation first. get_the_author_meta()
does not require any arguments, but you can supply the field you wish to be returned. get_author_posts_url()
requires the user_id. get_author_posts_url()
and this one is a bit more flexible and will take a user_id or various Objects.
The code sample below should work…
$author_id = get_the_author_meta( 'ID' );
$author_link = get_author_posts_url( $author_id );
$author_avatar = get_avatar_url( $author_id );
$featured_image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' );
echo '<div>
<div class="">
By <a href="' . esc_url( $author_link ) . '">Author</a>
</div>
</div>';