How to transfer all requests to index.php through htaccess, except for 404?

Question

htaccess

I need all requests to be redirected to index.php, and in case of a response, the server 404 is redirected to 404.html.

Tried like this:

RewriteEngine on

RewriteCond %{REQUEST_URI} !^/templates/
RewriteCond %{REQUEST_URI} !^/uploads/
RewriteCond %{REQUEST_URI} !^/panel/
RewriteCond %{REQUEST_URI} !^/ajax/

ErrorDocument 404 /404.html

RewriteRule ^((?!index\.php).+)$ /index.php [L]

But when the server responds with a 404 code, nothing happens.