Drupal 8.x

I have installed several times successfully in two subdirectories, but whenever I attempt to go to another page i get the https://www.modelsushi.com/core/install.php (drupal is already installed page)

I have followed this tutorial drupal 8 multisite
changed permissions Step 3

I'm trying to develop an empty module in drupal8 to understand the difference comparing it with Drupal7.

I would like to know how it is possible to insert javascript.

In drupal 7 I used this two instruction:

drupal_add_js('files.js',array('cache' => false));
drupal_add_js('jQuery( document ).ready( function(){somefunction();});','inline');

In drupal 8 drupal_add_js is deprecated. Is there other method to execute somefunction when the document is ready?

I've entered the trusted host patterns code in settings.php:

Drupal: 8.0.0-RC2
O/S: Centos 6.7
PHP: 5.6.14
MySQL: 5.5.46

I'm installing Drupal 8 on my Centos 6 server. To do this I needed to upgrade both PHP and MySQL. However, I'm now getting the following error message from the installer:

The libmysqlclient driver version 5.1.54 is less than the minimum required version. Upgrade to libmysqlclient version 5.5.3 or up, or alternatively switch mysql drivers to MySQLnd version 5.0.9 or up.

I am a web designer that has been hired by a company to rebuild their website. I have hand coded the site, and its 90% done but now they are asking my to move it over to Drupal because the head devs want to start implementing it as a CMS. I have never used Drupal before, and I am having a real hard time understanding what I have to do to get the site operational. I am overwhelmed with the capabilities of Drupal, and I really don't need most of the extra's that are available. I have tried to watch tutorials, I have tried installing themes and editing them but I am really getting no where.

So I have two sites with drupal 8 commerce one which is my main site, and the other which had an install in a subdirectory, and a third with just a basic install with a few modules like admin toolbar.

I was able to update the subdirectory installation flawlessly had no other modules in it. When I attempted to update the root installation i got server error 500. At first I thought it was my configuration and or htaccess file. I could not get this error