A friend from cbox.dk had the solution for me, so added this to the themes funxtions.php:
remove_filter('template_redirect', 'redirect_canonical');
And it works!
Worked a bit more on it and got following now.
Virtual host file:
ServerName http://mylivedomain.net/blog
ServerAlias my.backend.domain.com
When I ran WP install for the first time it still went back to the backend url, I switched that:
WordPress Address (URL) http://mylivedomain.net/blog
Site Address (URL) http://mylivedomain.net/blog
And also edited other references in the DB.
The site loads scripts and images on index.php now, but still goes back to my.backend.domain.com when I click links.
Tried then to force the WP and SITE URL’s via wp-config, it still tries to use the backend url.
Is there some way to force it to use the live url always?
I have two other WP installations with their own root folders and databases that need to run under the same conditions from the same backend server, so I can not have anything globally on the server, it needs to be done directly on each WordPress installation and the Apache VirtualHost that belongs to it.