Which license for KK s61 MK1

The first thing you should do is get a copy of Komplete Start which is free of charge. That gives you a selection of instruments and sounds. You can get that here - https://www.native-instruments.com/en/products/komplete/bundles/komplete-start/

The S61 MK1 is now end of life and doesn't work with the latest version of Komplete Kontrol. The good new is that the previous version (2.9.6) still works fine and you can download it from here - https://support.native-instruments.com/hc/en-us/articles/360000313457-Komplete-Kontrol-Legacy-Installers-for-Older-Operating-Systems

You need to download and install all the software in Komplete Start apart from Komplete Kontrol using Native Access, then install the 2.9.6 version of Komplete Kontrol. Native Access will tell you there's an upgrade for KK, just ignore it.