You have to enter serial number of K9 to Native Access. NA should authorise K9 to run on your computer. You must enter to NA the same credentials that you use for NI account where the licence for K9 is registered.
Service Center is not supported any more, it cannot be used for NI SW authorisation. It has no access to NI servers anymore.
If you meant to activate them with serial numbers, you can find them inside your account on NI website.
Let me know if you need more info or if I missed something.
Hard to say, if newer versions are needed. I guess no, as I have used SC alongside NA1 and it did work.
If the problem is demo mode, check also this article to see if it’s useful
https://support.native-instruments.com/hc/en-us/articles/4402377887121-My-Products-Are-Showing-As-DEMO-in-Native-Access
Prior to opening in a DAW always try the app as standalone first ! Else look at support article provided by LostInFoundation