I have installed new VM and put in /etc/init.d my test123.sh script which has LSB header and started it as a daemon service and of course the systemd doesn't recognize it via using systemctl status test123,however if I restart and type : systemctl status test123 ,it shows me active and the path to /etc/init.d .How did systemd recognize it?Shouldn't I first do systemctl enable test123.sh and then to expect to be recognized by the systemctl commands.I am using Linux Suse 12.2 . I seem to have in run/systemd/generator.late test123.service which I haven't put there.

systemd will automatically generate system unit files on the fly for init scripts when the system is started. This is why your script was recognized after the system was restarted and why test123.service file now exists. As far as I know systemd requires scripts to have the complete LSB header but it will try to determine priorities if incomplete or without them and may automatically enable your script.

Does this happens for all distros and versions which have systemd ,or there are exceptions?

I assume so. I don't know if any changes have been made to this functionality between systemd versions.