if ( have_posts() ) :
$i = 1;
while ( have_posts() ) :
the_post();
if ( in_array( $i, array( 3, 4 ), true ) ) {
# шаблон для 3 и 4 поста.
} else {
# шаблон для остальных постов.
}
$i++;
endwhile;
endif;
get_query_var()
global $wp_query;
$count = $wp_query->post_count;
global $wp_query;
$count = $wp_query->found_posts;
$args = array(
'posts_per_page' => -1,
'fields' => 'ids',
);
$posts = get_posts( $args );
$count = count( $posts );
wp_title()
, аthe_title()