It's the '5.3 Setup of virtual host for Moodle' that's tripping you up.
In that tutorial/how to it assumes you want each instance of whatever to use a different Fully Qualfied domain name.
The default virtualized site document root is curently set/in /var/www/html/moodle/
If you were change that back to /var/www/html/
And check/edit the config.php file in /var/www/html/moodle/ to make sure it's pointed to http://IP_address/moodle Make sure it works ... can login, etc.
then one could clone the code directory to something like moodle2.
cp -rp moodle moodle2 (dups the code)
cd /var/www/ ... this is where moodledata resides
cp -rp moodledata moodle2data (this dups the data directory)
Edit the config.php file in moodle2 for all the changes ... DB user, DB pass could remain the same *IF* you have set up the second database to use the same credentials. In this case, might be best to use the 'superuser' credentials for both instances of moodle.
Also edit the URL: http://IP_address/moodle to http://IP_address/moodle2
That way ... the base url to your site is http://IP_address/ ... which right now would/should beget the welcome screen until you put and index.html file in /var/www/html/ That file has two links ... one to /moodle/ and one to '/moodle2/.
To access directly, http://IP_address/moodle/
** Now if these are to be productions would highly recommend setting up *true* DNS entry so that the site is accessed via http://FQDN/
And, Moodle is moving towards requiring https ... so that's another consideration ... that would have to be addressed right after getting a valid FQDN for the server ... a true certificate from a CA.
Despite what directions one might find for installing Moodle, IF I know the site will be accessed from the internet by FQDN, I'll do that step first - DNS. Then get a valid CA for the server and make sure the server responds to access on port 443 ... *even before I begin a fresh install of a Moodle*.
'spirit of sharing', Ken