htaccess redirect subdomain to directory - .htaccess

Question

I need help to write proper rewrite rules in my htaccess files.
I need to redirect something like fr.example.com to example.com/fr, because we recently changed the whole website and the multilingual system is managed differently. The structure and the pages too.
I managed to do that successfully with this piece of code:
RewriteCond %{HTTP_HOST} ^fr\.example\.com [NC]
RewriteRule (.*) http://example.com/fr/$1 [L,R=301]
My problem now is to write something more specific for pages, for example :
fr.example.com/discover/foo should go to example.com/fr/bar/foo (different path, nothing consistant)
BUT ! example.com/discover/foo should go to example.com/bar/foo (end of the url is the same in both english and french)
Right now, since I have some common 301 redirects, the french urls aren't redirect properly and lead to the english pages. For example that one :
Redirect 301 /discover/foo /bar/otherfoo
Successfully redirects example.com/discover/foo to example.com/bar/otherfoo but also redirects fr.example.com/discover/otherfoo
How can I write two different rules for english and french? I'll have to write a bunch of different rules since everything is very different from the old subdomain to the new directory, I don't mind.
Thanks !
EDIT
Please note that it's for a wordpress installation, and the htaccess starts with :
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

Answer 1

First the these rules:
RewriteCond %{HTTP_HOST} ^fr\.example\.com [NC]
RewriteRule (.*) http://example.com/fr/$1 [L,R=301]
should look like this :
RewriteCond %{HTTP_HOST} ^(www\.)?fr\.example\.com [NC]
RewriteRule (.*) http://example.com/fr/$1 [L,R=301]
In order to capture bot www & non-www requests for subdomain.
Also this rule :
Redirect 301 /discover/foo /bar/foo
Will capture both requests to domain and sub-domains and using mod_rewrite here is correct not mod_alias so , replace this line with :
RewriteCond %{HTTP_HOST} ^(www\.)?example\.com [NC]
RewriteRule ^discover/foo http://example.com/bar/foo [L,R=301]
RewriteCond %{HTTP_HOST} ^(www\.)?(fr)\.example\.com [NC]
RewriteRule ^discover/foo http://example.com/%2/bar/foo [L,R=301]
Note: clear browser cache then test.