Possible to add “Template” selector to pages? Is Any Plugins are There..?

WordPress has this built in. As long as you have a page template created in PHP it will give you an option to use the template when creating a new page.

You can create a page template by adding this short snippet to the top of your PHP file.

<?php /* Template Name: Example Template */ ?>

For example, you could copy page.php and add the above code, then make any template specific changes and you will have a new page template.

Something like this…

<?php /* Template Name: Example Template */ ?>

<?php get_header(); ?>

<main>
    <div class="container clearfix">
        <?php
            while (have_posts()) :
                the_post();
                get_template_part('template-parts/content', 'page');
            endwhile; // End of the loop.
        ?>
    </div> <!-- /container -->
</main>

<?php get_footer(); ?>

Here is what it looks like in WP 5.2.2 admin.

You should defiantly read up on PAGE TEMPLATES.