Error in .htaccess file for removing index.php after upgrading to php v5.5 - apache

Question

I am using codeigniter framework. I tried to remove index.php, it was success. For some reason I need to upgrade php version to v5.5. Then I copy pasted same code for .htaccess then its not working now. Throws an error like below:
.htaccess file has following code and its on root folder outside application.
<IfModule mysql_auth_module>
AuthType Basic
AuthName "MySQL Member Page"
Auth_MYSQLhost www.kaoscms.eo
## Auth_MYSQLusername grafikkaos_kaoscms
## Auth_MYSQLpassword gJcY3xju}:XP
## Auth_MYSQLgrp_table
Auth_MYSQLdatabase grafikkaos_kaoscms
Auth_MYSQLpwd_table ks_users
Auth_MYSQLuid_field username_usr
Auth_MYSQLpwd_field password_usr
## Auth_MYSQL_EncryptedPasswords off
require valid-user
</IfModule>
<IfModule mod_rewrite.c>
RewriteEngine On
#RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^admin/(.*)$ admin.php/$1 [L]
RewriteRule ^admin/$ admin.php [L]
RewriteRule ^admin$ admin.php [L]
#RewriteRule ^install/(.*)$ install.php/$1 [L]
#RewriteRule ^install/$ install.php [L]
#RewriteRule ^install$ install.php [L]
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteRule ^admin(.*)$ admin.php [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteRule ^install(.*)$ install.php [L]
</IfModule>
<IfModule mod_rewrite.c>
# Turn on URL rewriting
RewriteEngine On
# If your website begins from a folder e.g localhost/my_project then
# you have to change it to: RewriteBase /my_project/
# If your site begins from the root e.g. example.local/ then
# let it as it is
RewriteBase /
# Protect application and system files from being viewed when the index.php is missing
RewriteCond $1 ^(application|system|private|logs)
# Rewrite to index.php/access_denied/URL
RewriteRule ^(.*)$ index.php/access_denied/$1 [PT,L]
# Allow these directories and files to be displayed directly:
RewriteCond $1 ^(index\.php|robots\.txt|favicon\.ico|public|assets|content|css|js|images)
# No rewriting
RewriteRule ^(.*)$ - [PT,L]
# Rewrite to index.php/URL
RewriteRule ^(.*)$ index.php/$1 [PT,L]
</IfModule>

Answer 1

Try this,it will fix your issue.
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /index.php/$1 [L,QSA]