Display posts from a specific category on frontpage.php template?

Question

I'm trying to display posts from specific categories. And I believe I have the correct code:

<?php if ( in_category('11') ) { ?>
     <div class="post"> 
          <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
          <div class="entry">
               <?php the_content(); ?>
          </div>
     </div>
<?php } ?>

I know there are posts in that category, because if I use the querystring ?cat=11 I can see them. Only not here. Nothing is showing. What am I doing wrong?

Edit: As requested, I'm posting the results from <?php print_r( $GLOBALS['post'] ); ?>

WP_Post Object ( [ID] => 10 [post_author] => 1 [post_date] => 2013-03-08 12:46:36 [post_date_gmt] => 2013-03-08 12:46:36 [post_content] => This is the content from my static frontpage.php [post_title] => Forside [post_excerpt] => [post_status] => publish [comment_status] => open [ping_status] => open [post_password] => [post_name] => forside [to_ping] => [pinged] => [post_modified] => 2013-03-12 07:30:56 [post_modified_gmt] => 2013-03-12 07:30:56 [post_content_filtered] => [post_parent] => 0 [guid] => http://vsandbox.net/wordpress/?page_id=10 [menu_order] => 0 [post_type] => page [post_mime_type] => [comment_count] => 0 [filter] => raw )

On a sidenote, I noticed in a different thread that someone had problems with this when not using it in single.php. I'm not even sure what that means. I mean, each layout of the webdesign has to be put in it's own page template php-file right?

Edit2: Here is the full code of the frontpage.php file:

<?php
/*
Template Name: Forside
*/
?>
<?php get_header(); ?>

            <div id="content">

                <div id="inner-content" class="wrap clearfix">

                    <div id="main" class="twelvecol first clearfix" role="main">

                    <!-- START LOOP -->
                    <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
        <?php print_r( $GLOBALS['post'] ); ?>
                    <section class="entry-content clearfix" itemprop="articleBody">
                        <?php the_content(); ?>
                    </section> <!-- end article section -->

            <p>Innlemmet 2011</p>
                        <?php if ( in_category('11') ) { ?>
                test
                                <div class="entry">
                                    <?php the_content(); ?>
                                </div>
            <?php } ?>

            <p>Innlemmet 2012</p>
                        <?php if ( in_category('12') ) { ?>
                            <div class="post"> 
                                <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
                                <div class="entry">
                                    <?php the_content(); ?>
                                </div>
                            </div>
            <?php } ?>

            <p>Innlemmet 2013</p>
                        <?php if ( in_category('12') ) { ?>
                            <div class="post"> 
                                <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
                                <div class="entry">
                                    <?php the_content(); ?>
                                </div>
                            </div>
            <?php } ?>

                        <!-- END LOOP -->
                        <?php endwhile; else: ?>
                        <p><?php _e('Sorry, no posts matched your criteria.'); ?></p>
                        <?php endif; ?>

                        </div> <!-- end #main --> 
                </div> <!-- end #inner-content -->

            </div> <!-- end #content -->

<?php get_footer(); ?>

Answer 1

Take a look at multiple loops for examples

And also look at the content.php file in the Twenty Fourteen theme

<?php

// The Query
$category_query = new WP_Query( 'category__in=11' );

// The Loop
if ( $category_query->have_posts() ) {
    echo '<ul>';
    while ( $category_query->have_posts() ) {
        $category_query->the_post();
        echo '<li>' . get_the_title() . '</li>';
    }
    echo '</ul>';
} else {

}
/* Restore original Post Data */
wp_reset_postdata();

Don't forget you can use pre_get_posts to alter an existing loop and exclude categories from any loop.

Answer 2

I assume that you are using this template on a page. So you forgot to query posts for the categories. the_post(); is reflecting to the page not posts.

<?php
$query = new WP_Query('cat=12');
if ($query->have_posts()) :
    ?><p>Innlemmet 2012</p><?php
    while ($query->have_posts()) : $query->the_post();
        the_title(); ?>
    endwhile;
endif;
?>

Read about the WP_Query class here (https://codex.wordpress.org/Class_Reference/WP_Query)