How to insert part of url via htaccess - regex

Question

I've got old URLs like this:
http://example.com/news/newscategory/77654
And it should be rewritten to this URL structure:
http://example.com/news/newscategory/id/77654
So the news is static here as it's the folder. the newscategory can be something else (multiple categories). And I want to redirect the user (301) to new url with id/ part.
I fetch the url via php where the news is key, newscategory is value, id is key and number at the end is again, value.
I'm using this htaccess for this:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
RewriteRule ^.*$ index.php [NC,L]
</IfModule>
Then I use some php library to fetch the values.
Edit: What I'm asking is that I want to redirect user from first url to second one so that I can fetch the id.
The first link is already working, but I still have links to the old url structure that leads to category view. Live urls:
old structure: http://www.autonet.ee/uudised/paevauudised/77665
new structure: http://www.autonet.ee/uudised/paevauudised/id/77665
the old one should redirect user to the new link.

Answer 1

You can use:
RewriteEngine On
# add /id/ in /news/... URLS
RewriteRule ^(news/[^\w-]+)/(\d+)$ /$1/id/$2 [R=301,L,NC]
# front controller rule
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ index.php [L]

Answer 2

Try this rule if i understand correctly
RewriteRule ^([.*])/([.*])/([.*])/([.*])$ index.php?$1=$2&$3=$4
please explain if missed something.
EDIT
okay, according to you news and id are static but their value is dynamic please try the rule below
RewriteRule ^(news)/([.*])/(id)/([.*])$ index.php?news=$1&id=$2