Unfortunately, Service Center 8 will not boot to DOS with UEFI enabled. We are working on the ability to do so, but at this time there exists no method to boot to a USB Device that doesn't have Windows or Linux on it.
In order to boot into DOS from our Multipurpose USB Device you will have to disable Secure Boot, and enable Legacy Boot Mode. Unfortunately not all devices that utilize UEFI have these options available. (Just a note that some systems only utilize one or the other, in this case you will not be able to find the other option)
Once you have made these changes try booting to the device again and things ought to work. Just for your information, this should also work with SC 7.5 for DOS.
As for your second concern, when you submitted for an upgrade to SC 8 you should have provided your information so that our sales team can contact you. This is due to the fact that upgrading from Service Center 7.5 to 8.0 is not a free upgrade and will require you to purchase an upgrade. We provide a free upgrade to the next version of Service Center, the release after that must be purchased.
I will make sure to let the sales department know that you are looking at SC 8, if you provide me with some contact info I can have them contact you directly.