htaccess one RewriteCond for multiple RewriteRules?

With your shown samples and attempts; please try following .htaccess rules file. As per anubhava's comments have added RewriteCond conditions before each RewriteRule.

Please make sure to clear your browser cache before testing your URLs.

RewriteEngine ON

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.com$ [NC]
RewriteRule ^(?:1|3)example$ /  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.com$ [NC]
RewriteRule ^(2|4)example$ /example$1  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.net$ [NC]
RewriteRule ^5example$ /sgsg  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.net$ [NC]
RewriteRule ^6example$ /example2  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.net$ [NC]
RewriteRule ^7example$ /  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.net$ [NC]
RewriteRule ^8example$ /example44  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.uk$ [NC]
RewriteRule ^9example$ /  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.uk$ [NC]
RewriteRule ^10example$ /example12  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.uk$ [NC]
RewriteRule ^11example$ /  [R=302,L,NC]

RewriteCond %{HTTP_HOST} ^(?:www\.)?example\.uk$ [NC]
RewriteRule ^12example$ /example41  [R=302,L,NC]

Fixes applied to OP's attempts:

• Attached 2 rules into 1 eg: RewriteRule ^(?:1|3)example$ / [R=302,L,NC] very first rule in above file.
• Added NC flag in both RewriteCond and RewriteRule in all of the rules.
• Made use of non-capturing group in RewriteCond to make www. optional eg: FROM ^(www\.example\.com|example\.com) TO ^(?:www\.)?example\.com$

As already mentioned, the RewriteCond (condition) directive itself applies only to the first RewriteRule that follows. The RewriteCond directive forms part of a single rule.

However, you can "workaround" this in various ways, without having to apply the same condition to multiple rules.

For example:

# Skip the following 4 rules when host is NOT "example.com"
RewriteCond %{HTTP_HOST} !^(www\.)?example\.com [NC]
RewriteRule ^ - [S=4]

# These rules only apply to "example.com"
RewriteRule ^1example$ /  [R=302,L]
RewriteRule ^2example$ /example2  [R=302,L]
RewriteRule ^3example$ /  [R=302,L]
RewriteRule ^4example$ /example4  [R=302,L]

# Skip the following 4 rules when host is NOT "example.net"
RewriteCond %{HTTP_HOST} !^(www\.)?example\.net [NC]
RewriteRule ^ - [S=4]

# These rules only apply to "example.net"
RewriteRule ^5example$ /sgsg  [R=302,L]
RewriteRule ^6example$ /example2  [R=302,L]
RewriteRule ^7example$ /  [R=302,L]
RewriteRule ^8example$ /example44  [R=302,L]

# Skip the following 4 rules when host is NOT "example.uk"
RewriteCond %{HTTP_HOST} !^(www\.)?example\.uk [NC]
RewriteRule ^ - [S=4]

# These rules only apply to "example.uk"
RewriteRule ^9example$ /  [R=302,L]
RewriteRule ^10example$ /example12  [R=302,L]
RewriteRule ^11example$ /  [R=302,L]
RewriteRule ^12example$ /example41  [R=302,L]

Alternatively, you could temporarily prefix the hostname to the URL-path and test for this directly in the RewriteRule directive.

For example:

# Prefix the hostname to the URL-path
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{HTTP_HOST} ^(?:www\.)?(example\.com|example\.net|example\.uk)
RewriteRule ^ %1%{REQUEST_URI}

RewriteRule ^example\.com/1example$ /  [R=302,L]
RewriteRule ^example\.com/2example$ /example2  [R=302,L]
RewriteRule ^example\.com/3example$ /  [R=302,L]
RewriteRule ^example\.com/4example$ /example4  [R=302,L]

RewriteRule ^example\.net/5example$ /sgsg  [R=302,L]
RewriteRule ^example\.net/6example$ /example2  [R=302,L]
RewriteRule ^example\.net/7example$ /  [R=302,L]
RewriteRule ^example\.net/8example$ /example44  [R=302,L]

RewriteRule ^example\.uk/9example$ /  [R=302,L]
RewriteRule ^example\.uk/10example$ /example12  [R=302,L]
RewriteRule ^example\.uk/11example$ /  [R=302,L]
RewriteRule ^example\.uk/12example$ /example41  [R=302,L]

# (OPTIONAL) Remove hostname prefix from URL-path
RewriteRule ^[^/]+/(.*) $1