All REPRISE licenses are backwards compatible. If a user/customer has a higher product version, also the lower product versions should work with the higher license (means, when a customer has ARES Commander 2020, everything back to ARES Commander 2017 should work with this license higher product version. Since the product version 2017 we introduced this new Internet WEB-activation. For products before 2017 the customer has to login with higher version once, to download the license and then start e.g. ARES Commander 2016 to run it with the standalone license).
For network licenses are backwards compatible too, but here the user/customer should remove the older license key versions from the NLM due to legal reasons, because otherwise he gets additional licenses from the previous versions, too and double each update the number of clients.