Display all posts from one category

Hi,

I am trying to put all of my posts from the “tutorial” category on a page. I have used this, but it does not work :

<?php
$catPost = get_posts(get_cat_ID("3")); //change this
   foreach ($catPost as $post) : setup_postdata($post); ?>

<h1><a>"><?php the_title(); ?></a></h1>
    <?php the_excerpt(); ?> 

<p class="postinfo">Written by: <?php the_author_posts_link(); ?>
Posted on: <?php the_time('F j, Y'); ?> at <?php the_time('g:i a'); ?>
Categories: <?php the_category(', '); ?></p>
<hr />
<?php  endforeach;?>

It also shows posts from other categories: https://mybluebox.dearestdesigns.com/?cat=3

I previously tried this one, but it says error on line 17.

<?php
// The Query
query_posts( array ( 'category_name' => 'tutorials', 'posts_per_page' => -1 ) );
?>

    <?php
// The Loop
while ( have_posts() ) : the_post();
	echo '<h1>';
	the_title();
	echo '</h1>';
	the_excerpt();
	echo ' <p class="postinfo">Written by: ';
	the_author_posts_link();
	echo 'Posted on '
	the_date();
	echo 'Categories: '
	the_category(', ');
	echo '</p>'
	endwhile; ?>

	  <?php

	  // Reset Query
	  wp_reset_query();

	  ?>