Running slim framework on existing apache web server

I am new to slim framework. Currently on my existing webserver which is on centos 7 I have other php based application running. So currently my directory structure is like this.

var/www/html
    phpapp1
    phpapp2
    apislim

The folder for the apislim I created was for slim framework. Below are the exact steps I did was

1. composer create-project slim/slim-skeleton

2. I rename the slim-skeleton folder to apislim

3. I make sure the owner is apache chown -R apache:apache apislim

4. In the httpd.conf I ensure this AllowOverride is enabled to be All

   <Directory "/var/www"> AllowOverride All # Allow open access: Require all granted Options -Indexes

Also below I enabled All

<Directory "/var/www/html">   
    Options -Indexes -FollowSymLinks
    AllowOverride All
</Directory>
  

5. In the apislim/public folder I have this .htaccess file as below.

<IfModule mod_rewrite.c>
  RewriteEngine On

  
  RewriteCond %{REQUEST_URI}::$1 ^(/.+)/(.*)::\2$
  RewriteRule ^(.*) - [E=BASE:%1]


  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^(.*)$ %{ENV:BASE}index.php [QSA,L]
</IfModule>

6. The I have also the index.php file in the public folder which also links up to the src for the routes and the main folder apislim I created another .htaccess file and added this.

   RewriteEngine on RewriteRule ^$ public/ [L] RewriteRule (.*) public/$1 [L]

The issue now I want my existing application to work along with this REST api which is based on Slim framework. So when I go to this link

http://*.*.*.*/apislim/
http://*.*.*.*/apislim/public/
http://*.*.*.*/apislim/public/index.php

Neither of it works all are giving me 403 forbidden. Then I check the error log it show error regarding FollowSymLinks So I added

Options -Indexes +FollowSymLinks 

into <Directory "/var/www/html">

So next error I get now is 500 interval server error.

The following steps are necessary for your Slim 3 application to work within subdirectories.

Directory structure:

• public/ Web server files (the DocumentRoot)
  • .htaccess Apache redirect rules for the front controller
  • index.php The front controller
• .htaccess Internal redirect to the public/ directory

The content of the file: .htaccess:

RewriteEngine on
RewriteRule ^$ public/ [L]
RewriteRule (.*) public/$1 [L]

The content of the file: public/.htaccess:

# Redirect to front controller
RewriteEngine On
# RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [QSA,L] 

Add this container entry to the file: dependencies.php:

// Activating routes in a subfolder
$container['environment'] = function () {
    $scriptName = $_SERVER['SCRIPT_NAME'];
    $_SERVER['SCRIPT_NAME'] = dirname(dirname($scriptName)) . '/' . basename($scriptName);
    return new Slim\Http\Environment($_SERVER);
};

Edit: In Slim 4 you should use the $app->setBasePath($basePath); method. More details