All pages are the same

Problem solved.

Here is what I did:

1. I Thought: the only custom post type that is showed correctly on back-end is the cpt “Informazione”. So maybe the problem is here
2. I’ve disabled this custom post type and effectively everything come back to work as aspected
3. Searching on the web I found that other users had the same problem. They solved adding a wp_reset_query() somewhere in their code. Me also I’ve tryed this solution before posting here, but without success. The difference was that now I knew that some query around the “Informazione” cpt was causing the problem
4. I’ve disabled some block of codes until I’ve found the problem:

functions.php

add_filter( 'pre_get_posts', 'my_get_posts' );
function my_get_posts( $query ) 
{
    if($query->get("page_id") == get_option("page_on_front")) 
    {
        $query->set("post_type", "informazione");
        $query->set("posts_per_page", -1);
        return $query;
    }
}

I was using this code in order to see in home page an “Informazione” post. I removed it and everything worked again.