RewriteEngine on
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteCond %{QUERY_STRING} ^c=(.*)$ [NC]
RewriteRule ^events.php$ http://www.yourdomain.com/plug.php\?e=events&c=%1 [L,R=301]

RewriteCond %{QUERY_STRING} ^f=old&c=(.*)$ [NC]
RewriteRule ^events.php$ http://www.yourdomain.com/plug.php\?e=events&f=old&c=%1 [L,R=301]

RewriteCond %{QUERY_STRING} ^f=upcoming&c=(.*)$ [NC]
RewriteRule ^events.php$ http://www.yourdomain.com/plug.php\?e=events&f=upcoming&c=%1 [L,R=301]

RewriteCond %{QUERY_STRING} ^m=details&id=(.*)$ [NC]
RewriteRule ^events.php$ http://www.yourdomain.com/plug.php\?e=events&m=details&id=%1 [L,R=301]

RewriteRule events.php$ http://www.yourdomain.com/plug.php\?e=events [R=301,L]