FLStudioMobile Android:
Please check the Google Play Store support on this subject: Download previously purchased & downloaded apps For FLStudioMobile iOS:
Please check the Apple iTunes support web site on this subject: Downloading past purchases ...
FLStudio for macOS was FLStudio 20 (May 2018)
You can download FLStudio for macOS and Windows from our FLStudio downloads page .
Purchasing FLStudio gives you a valid licence to use both macOS and Windows versions ...