Directing read more to expand post on same multi-post page

Thank you in advance.

url: https://ourconstitutionalrights.com/in-the-news/ — Default Kubrick theme

I’m trying to understand the workings of the read more function. I added it to this page using the quicktag.

The codex Customizing the Read More features this template tag: <?php the_content( $more_link_text , $strip_teaser, $more_file ); ?>

Searching the default theme’s templates shows <?php the_content(‘<p class=”serif”>Read the rest of this entry »</p>’); ?> in the image.php, index.php and page.php…all without the parameters mentioned.

Question: are these parameters generated code? From which template? Should I add them manually? Can I control which page the full post opens in?

Question: is it possible to have the expanded post appear in the same non-single multiple post front page when the excerpt first appeared…instead of jumping to a single page?

Question: Is using a plug-in advisable for someone with little php experience?

Note: As you’ll see, I have work to do to get my single page set up. I was not planning in using it.

Thanks to all. I hope to return the favor someday.