How to write htaccess rewrite rule for redirecting pages which doesn't exist to 404 page

I mentioned my htaccess rewrite rule below


If I enter a wrong url, for example:

'http://example.com/hosting/web-hosti' directs to 'http://example.com/main-page.php?pagename=web-hosti' where 'web-hosti' page doesn't exist.

or

'http://example.com/contac' directs to 'http://example.com/sub-page.php?pagename=contac' where 'contac' page doesn't exist.

Can anyone please tell me how to redirect all wrong urls to 404 page?

RewriteEngine ON

##Rules for existing php files rewrite.
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^(.*)/?$ $1.php [NC,L]


RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^hosting/(.*)/?$ main-page.php?pagename=$1 [NC,L]


RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/?$ sub-page.php?pagename=$1 [NC,L]

ErrorDocument 404     /404.php
RewriteCond %{REQUEST_URI} ^/404/$
RewriteRule ^(.*)$ /404.php [L]