internet access to my site

Hi
to begin, I am a newbie 🙂
I have installed wordpress on my synology NAS. I use a multi-site configuration.
It is working well in my local network (http://192.168.1.12/wordpress/…) but I have difficulties to make it visible from internet.

First, I dont understand why from the configuration panel (http://192.168.1.12/wordpress/wp-admin/options-general.php), in the general settings I don’t have the options WordPress address & site address…

I have tested to modify the wp-config.php file replacing
define(‘WP_HOME’,’http://mydomaine.biz/wordpress’);
define(‘WP_SITEURL’,’http://mydomaine.biz/wordpress’);
and It doesn’t work…

Second, is it possible to access from the local network & the internet at the same time ?

thanks a lot

Dave