Routing to production and testing Drupal installations on shared hosting account
Most shared hosting plans have a feature called subdomains or addon domains (these features exists in cpanel plans for sure. I m attaching a screenshot from a godaddy hosting plan). You may use this feature to effectively create a new apache virtual host so you dont have to mess with the .htaccess file to do the routing depending on the domain name

Also note that most shared hosting providers do not support overriding many features using the .htaccess file so many on of the options in your .htaccess file may be ignored depending on the apache configuration file (which you usually do not control)

Also note that .htaccess is an Apache concept. If your hosting provider uses another http server (e.g. nginx or IIS) the .htaccess file will be totaly ignored.

Last if you really want to do this with .htaccess (i dont recomend this) make sure you dont miss the query option in any of your cases. Notice the last part here index.php?q=$1  the ?q=$1 part is very important