Trying hard but can’t hide featured post/page from grid

wp section of stackexchange really seems half dead.

you rarely get issue sorted.

have_posts checks whether there is any post, so add another condition that checks whether the post is featured or not.

if(have_posts()) :  while(have_posts()) :  the_post();

replace above with below

if(have_posts() && the_post() != $featured) :  while(have_posts()) :  the_post();