Wordpress is showing paginated pages that doesn't exist - pagination

Question

I have a page template where I run a WP_Query
$temp = $wp_query;
$wp_query= null;
$wp_query = new WP_Query();
$wp_query->query('post_type=post&posts_per_page=4'.'&paged='.$paged);
while ($wp_query->have_posts()) : $wp_query->the_post();
The issue I'm facing is that if you go to the site /page/100 it will show the template and it's not going to a 404 when It should.
My blog page under reading settings is another page and this is a custom template I'm doing.
I have read this post https://wordpress.stackexchange.com/questions/46116/non-existing-blog-pages-are-not-redirected-to-404 and tried all the functions and none of them work.
I also spent 3 hours searching on google without being able to find a workaround.

Answer 1

You are creating a new WP Query. So I think you have to reset the wp_postdata.
WP Codex offers sample code. You could try something like
$wp_query = new WP_Query();
$wp_query->query('post_type=post&posts_per_page=4'.'&paged='.$paged);
if( ($wp_query->have_posts() ) :
while ($wp_query->have_posts()) : $wp_query->the_post();
// Do here something with the post
endwhile;
wp_reset_postdata(); // At the end reset your query
endif;

Answer 2

While using WP_Query for displaying posts list you need to check by yourself if they are any posts for current page. Below is example code from Wordpress docs
<?php if ( have_posts() ) : ?>
<!-- Add the pagination functions here. -->
<!-- Start of the main loop. -->
<?php while ( have_posts() ) : the_post(); ?>
<!-- the rest of your theme's main loop -->
<?php endwhile; ?>
<!-- End of the main loop -->
<!-- Add the pagination functions here. -->
<div class="nav-previous alignleft"><?php next_posts_link( 'Older posts' ); ?></div>
<div class="nav-next alignright"><?php previous_posts_link( 'Newer posts' ); ?></div>
<?php else : ?>
<p><?php _e('Sorry, no posts matched your criteria.'); ?></p>
<?php endif; ?>
Replace " _e('Sorry, no posts matched your criteria.'); "
with own error or function displaying 404 error.
Edit: Above code is of course example for Main Loop. In your particular case you need to call $wp_query->have_posts() and make sure it not evaluates to false. If it does display 404 error.
for example:
if(!$wp_query->have_posts()) {
echo "404";
}
Or if you want server respond with HTTP code 404 instead of 200 then you should try something like this:
if(!$wp_query->have_posts()) {
status_header(404);
nocache_headers();
include( get_404_template() );
exit;
}