Joms

I recommend using an array for your arguments to make it easier to read. So with your query try this instead:

$args = array(
	'post_type' => 'plants',
	'posts_per_page' => 999, //if you intend to show all posts you can just use -1 here instead
	'orderby' => 'title',
	'order' => 'ASC	',
	'tag__not_in' => array( 12,22 )
);

Just for context why/where do you want to flush the rewrite rules? If it’s for a plugin I suggest calling flush_rewrite_rules() on plugin activation/deactivation. You can find some code snippets here: https://codex.wordpress.org/Function_Reference/flush_rewrite_rules

Try this: https://codex.wordpress.org/Updating_WordPress#Manual_Update

Yes but you have to put the code of contact_search.php ON the same file as the HTML code as well.

You will just then need a condition to determine that your form has been posted. Something like:

if ( isset( $_POST['submit'] ) ) { //the form has been submitted, process the data
  //place your contact_search.php code here
} else { //the form has not yet been submitted
  //show your form here (HTML)
}

Then change your form action to "" so the form will post to itself. No need to point it anymore to contact_search.php since it’s inside your file.

It’s because you are posting to http://www.lamartinierelucknow.org/contact_search.php and that means the file should be at your WP’s root directory.

A better way to achieve what you want is to create a custom page template inside your theme. Then assign that template to a WordPress Page. The template file will then have both your PHP code and HTML for the form.

Here are some examples that could help you get started:
http://www.webdesign.org/how-to-create-contact-page-template-in-your-wordpress-theme.22210.html
http://www.paulund.co.uk/creating-wordpress-custom-page-templates

You forgot to use the $args array. Change query_posts() to query_posts($args). I also suggest adding wp_reset_query() after the loop.

For more info: https://codex.wordpress.org/Function_Reference/query_posts

The images are in the wp-content/uploads directory. This is a sample image on your website which is missing:

http://girodilento.com/wp-content/uploads/2016/01/DSC03771-1038×576.jpg

You can try to check that file through FTP.

Some files might have gotten corrupted when the automatic update was done. You can try a manual update via FTP. Follow the guide here: https://codex.wordpress.org/Updating_WordPress#Manual_Update

You can also try deleting the .htaccess file found in the root directory of your site. This can be the cause of the redirect problem. Make sure to create a backup of it first so you can restore it later if something goes wrong.