It looks like you will need to reinstall 9.353-004 in order to install the beta. But this does make me wonder if the the 9.4 Beta has the security updates released in 9.354.
Well .. for a demo environment and utm playgroud installation, you could edit /etc/version.
Just "downgrade" to 9.353-4 and you can install 9.370.
Since 9.354 contains mainly security fixes .. rpm does not complain about version issues, but I won't recomand this "workaround" for production environments ! :)