pichichi

Can you access any of the broken image directly at the image URL in a browser?

Do you use a content delivery network like cloudflare or jetpack? Do you know if you have any caching enabled with your host, or have caching set by your theme or plugin? Media suddenly appearing to vanish without user input is often a problem between those kind of services.

Does loading the site on a differnet device or a browser mode like Chrome’s Incognito mode make a difference?

De nada.

If you have access to your functions.php file, adding this snippet will give you a new shortcode [print_my_breadcrumb].

Using this with the shortcode block will print a bradcrumb trail.

function print_my_breadcrumb_shortcode() {
    // Get the global post variable
    global $post;
    // Get the home URL for the "Home" link in the breadcrumb
    $home = get_bloginfo('url');
    // Initialize the output variable with the "Home" link
    $output = '<a href="' . $home . '">Home</a>';
    // Check the current post type and add the appropriate links to the breadcrumb
    if (is_page() || is_single()) {
        // Add a link to the parent page
        $output .= ' / <a href="' . get_permalink($post->post_parent) . '">' . get_the_title($post->post_parent) . '</a>';
        // Add the current page title
        $output .= ' / ' . get_the_title();
    } elseif (is_category() || is_tax()) {
        // Add the current category or taxonomy title
        $output .= ' / ' . single_term_title('', false);
    } elseif (is_tag()) {
        // Add the current tag title
        $output .= ' / Tag: ' . single_tag_title('', false);
    } elseif (is_year()) {
        // Add the current year
        $output .= ' / ' . get_the_time('Y');
    } elseif (is_month()) {
        // Add the current month and year
        $output .= ' / ' . get_the_time('F Y');
    } elseif (is_day()) {
        // Add the current day, month, and year
        $output .= ' / ' . get_the_time('F j, Y');
    } elseif (is_author()) {
        // Add the current author name
        $output .= ' / Author: ' . get_the_author();
    } elseif (is_search()) {
        // Add the current search query
        $output .= ' / Search Results for: ' . get_search_query();
    } elseif (is_404()) {
        // Add a "404 - Page Not Found" message
        $output .= ' / 404 - Page Not Found';
    }
    // Return the breadcrumb trail
    return $output;
}
// Register the shortcode
add_shortcode('print_my_breadcrumb', 'print_my_breadcrumb_shortcode');

By default WordPress does a fuzzy match on anything typed as a URL, you can turn this off by adding the following code to your functions.php file:

add_filter( 'strict_redirect_guess_404_permalink', 'stop_the_fuzzy_redirects_please');

function stop_the_fuzzy_redirects_please() {
  return true;
}

Source: https://developer.wordpress.org/reference/hooks/strict_redirect_guess_404_permalink/

For (1) You could use a plugin like https://wordpress.org/plugins/if-so/ to only show the page if a user is logged in.

I should have mentioned, you can show and hide Divi modules based on logged in status. Go to any module’s options, Advanced>Conditions>Display Contitions>User Logged In

Not directly, but…

Some hosting companies have a “staging area”, check to see if yours does. This is basically a copy of your site you can experiment with and it doesn’t affect your main site until you are ready to push the changes.

Another way is to download your site and work on it on your computer. There are 2 main ways to do this, one is using containers (Search the web for WordPress and Docker) and the other is setting up a server on your computer, install WordPress and import your site (Search the web for WordPress and MAMP). Once you are happy you can either upload your new theme or the entire site you have on your computer. This can be quite daunting but you would learn lots of new skills.

To explain the steps involved would be out of the scope of a reply, but those are the basics and should point you in the irght direction. MAMP and Docker are given as examples to point you in the right direction, these are not reccomendations to use those particular sevices.