htacess Proxy Redirect /a to /b, 301 redirect of /b to /a - apache

Question

I have website built on a bespoke centralised legacy CMS.
It has a section which works under the URL /database
For one site I'd like to change that to use /blog and it still needs to tell the CMS that it's database.
So for .htaccess I have
RewriteRule ^blog$ /database [P,L]
RewriteRule ^blog/(.*)$ /database/$1 [P,L]
Which works great. But I also need to tell google that the site has changed and not to look at the old one.
So I need /database to 301 to /blog.
So:
RewriteRule ^database$ /blog [L,R=301]
I've tested this with http://htaccess.madewithlove.be and it says it's fine, but it's causing an infinite loop in the browser.
To be honest I feel like part of the problem is that I can't really express the question very well, especially the title, so any feedback on that would be appreciated.
Here's the rest of the file just in case that's relevant
# redirect trailing slashes
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{QUERY_STRING} ^(.+)?fromMobile=true$ [NC]
RewriteRule (.*) /$1?%1&%2 [R=301,L]
RewriteRule ^(.+[^/])/$ http://%{HTTP_HOST}/$1 [R=301,L]
#uk.com
RewriteEngine On
RewriteCond %{HTTP_HOST} ^iflg\.uk\.com$ [NC]
RewriteRule ^(.*)$ http://www.iflg.uk.com/$1 [R=301,L]
RewriteRule ^blog$ /database [P,L]
RewriteRule ^blog/(.*)$ /database/$1 [P,L]
#RewriteCond %{REMOTE_ADDR} !=localhost
#RewriteRule ^database$ /blog [L,R=301]
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php
</IfModule>
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /~iflg/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /~iflg/index.php
</IfModule>

Answer 1

You need to exempt the second rule to prevent the proxy server from being redirected too.
RewriteCond %{REMOTE_ADDR} !=127.0.0.1
RewriteRule ^database$ /blog [L,R=301]
Do not rely on that htaccess tester, it is too simplistic.