I am using Sitecore 8.2 license file with Sitecore 9. I can see Sitecore.xDB.Base in the list of installed licenses but I am not sure if this is sufficient. Can use of Sitecore 8.2 licenses suppress some of the Sitecore 9 (or any module) functionalities?
No, the Sitecore 8.2 license file is the same as the one used for 9. Anything licensed under 8.2 should continue to be licensed under 9.
One exception could be the JSS server jss.sitecore.net/#/requirements May 1, 2018 at 0:23
And Device Detection is included as standard in Sitecore 9.0 now, which also requires a valid license (and may therefore need to be updated)– jammykamMay 1, 2018 at 13:46
I would also warn that not all licenses are the same. Licenses can vary and some 8.2 licenses do not work on 9 installs depending on how your license was procured.– Pete Navarra ♦Dec 21, 2018 at 23:38