I have been trying to change my code from my index.php to a custom page template instead as this is better practice I have been told.

The original code for the index.php does not work anymore so I have tried to this code, and it retrieves the posts correctly - however it appears to be retrieving the posts in 'Singular' format and displays all of the content rather than an excerpt.

Here is the current homepage php code:

<h3>Read Our Latest Cleaning Posts</h3>
    <div id="primary" class="content-area">
        <main id="main" class="site-main">
            <div id="blog-homepage">
            <?php
            $query_options = array('posts_per_page' => 3);
            $the_query = new WP_Query( $query_options ); 

            while ($the_query -> have_posts()) : $the_query -> the_post(); 
                get_template_part( 'template-parts/content', get_post_type() );

            endwhile;
            the_posts_navigation();
            wp_reset_postdata(); ?>
            </div>
        </main>
    </div>

And here is the template-parts/content file:

<div class="article-container">
    <?php scores_post_thumbnail(); ?>
<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
    <div class="post-text">
    <header class="entry-header">
        <?php
        if ( is_singular() ) :
            the_title( '<h1 class="entry-title">', '</h1>' );
        else :
            the_title( '<h2 class="entry-title"><a href="' . esc_url( get_permalink() ) . '" rel="bookmark">', '</a></h2>' );
        endif;

        if ( 'post' === get_post_type() ) :
            ?>
            <div class="entry-meta">
                <?php
                scores_posted_on();
                scores_posted_by();
                ?>
            </div><!-- .entry-meta -->
        <?php endif; ?>
    </header><!-- .entry-header -->

    <div class="entry-content">
        <?php
        if ( is_singular() ) :
        the_content( sprintf(
            wp_kses(
                /* translators: %s: Name of current post. Only visible to screen readers */
                __( 'Continue reading<span class="screen-reader-text"> "%s"</span>', 'scores' ),
                array(
                    'span' => array(
                        'class' => array(),
                    ),
                )
            ),
            get_the_title()
        ) );
        else :
            the_excerpt();
        endif;

        wp_link_pages( array(
            'before' => '<div class="page-links">' . esc_html__( 'Pages:', 'scores' ),
            'after'  => '</div>',
        ) );
        ?>
    </div><!-- .entry-content -->

    <footer class="entry-footer">
        <?php
        if ( is_singular() ) :
         scores_entry_footer();
        else: ?>
            <div>
                <a href="<?php the_permalink(); ?>">Read More</a>
            </div>
        <?php endif ?>
    </footer><!-- .entry-footer -->
    </div><!-- end of the text content container (excl. img tmb) -->
</article></div><!-- #post-<?php the_ID(); ?> -->

From what I gather the 'is_singular' is resulting in true, therefore causing it to display all the content. What am I doing wrong here?

--> Bonus: the code that did work on the index.php page but not on the custom template:

<h3>Read Our Latest Cleaning Posts</h3>
    <div id="primary" class="content-area">
        <main id="main" class="site-main">
            <div id="blog-homepage">
                <?php
        if ( have_posts() ) :

            if ( is_home() && ! is_front_page() ) :
                ?>
                <header>
                    <h1 class="page-title screen-reader-text"><?php single_post_title(); ?></h1>
                </header>
                <?php
            endif;

            /* Start the Loop */
            while ( have_posts() ) :
                the_post();

                /*
                 * Include the Post-Type-specific template for the content.
                 * If you want to override this in a child theme, then include a file
                 * called content-___.php (where ___ is the Post Type name) and that will be used instead.
                 */
                get_template_part( 'template-parts/content', get_post_type() );

            endwhile;

            the_posts_navigation();

        else :

            get_template_part( 'template-parts/content', 'none' );

        endif;
        ?>
            </div>
        </main><!-- #main -->
    </div><!-- #primary -->