RHEL7 reinstallation

Hi, I plan to do the system reinstallation, so would like to know before the installation:
1) Do I need to unregister the subsciption on system locally first before the reinstallation? Or there's no need to unregister the system and I can register again on first boot after the installation done?
2) Is that possible to create a local DVD with my own kickstart.cfg? If yes, then how's that? I tried to put my own kickstart.cfg into isolinux folder but failed to load. I'm not sure if the way I did is correct.

Thanks.