You have to write custom code to get the attachment id and post_parent by name(slug).

Put the below code in your theme's **functions.php** file

    if( ! ( function_exists( 'wp_get_attachment_by_post_name' ) ) ) {
	    function wp_get_attachment_by_post_name( $post_name ) {
		    $args = array(
			    'post_per_page' => 1,
			    'post_type' 	=> 'attachment',
			    'name' 			=> trim ( $post_name ),
		    );
		    $get_posts = new Wp_Query( $args );
		
		    return $get_posts->posts[0];
	    }
    }

then you can call the function where you need it like below :--

    $attachment = wp_get_attachment_by_post_name( $post_name );
    // Replace post_name by the name/slug of the attachment
    // It will give you an object, which you can render like below to get the ID and post_parent
    echo $attachment->ID; // Gives the id of the attachment
    echo $attachment->post_parent; // Gives the post_parent id
    echo $attachment->post_title; // Gives the attachment title.