.htaccess - 从重定向中排除文件

I want to exclude some files from redirecting but it still redirects to desktop site. Here is my code from .htaccss of mobile.website.com.

RewriteEngine On
RewriteCond %{REQUEST_URI} !^/Singers/singer\.php
RewriteRule ^(admin|user)($|/) - [L]
RewriteCond %{HTTP_HOST} ^mobile\. [NC]
RewriteCond %{HTTP_USER_AGENT} !(android|blackberry|googlebot-mobile|iemobile|iphone|ipod|opera\smobile|palmos|webos) [NC]
RewriteRule ^ http://www.website.com%{REQUEST_URI} [L,R=302] 

When user visits mobile.website.com/Singers on desktop, he is redirected to www.website.com/Singers.

I want to use mobile.website.com/Singers/singer.php to copy and manage files. I use www.website.com/admin/index.php to submit data to mobile.website.com/Singers/singer.php but it is redirected to www.website.com/Singers/singer.php without copying the files.