Change /discussions/ url-name

Hello,
I want to change discussion url
http://www.example.com/discussion/87/sephora-beauty-event-20-off-starts-11-3 to
http://www.example.com/to/87/sephora-beauty-event-20-off-starts-11-3

I have changed in .htaccess file is
RewriteEngine On

# Certain hosts may require the following line.
# If vanilla is in a subfolder then you need to specify it after the /.
# (ex. You put Vanilla in /forum so change the next line to: RewriteBase /forum)
# RewriteBase /

RewriteCond %{QUERY_STRING} ^p=/?([^&]+)(&([^?]+))?$
RewriteRule ^index\.php %1?%3 [E=X_REWRITE:1,L]
RewriteRule ^discussion/(.*)$ /to/$1 [R,L]
RewriteRule ^to(.*) index.php\?p=discussion$1 [PT,L]

and also add line in config file
$Configuration['Garden']['RewriteUrls'] = TRUE;

by changing this page is redirect but got error

This page isn’t working

www.example.com redirected you too many times.
Try clearing your cookies.
ERR_TOO_MANY_REDIRECTS
reload

As the requirement is a bit urgent, solution shall be highly appreciated. Thank you!