I have purchased a number of style packs to use in Capture One 11 and 12. Will those simply work in Capture One 20? Can I use those in older versions of the software as well?
After you have purchased and downloaded style packs, you need to import those into Capture One.
As Capture One Styles were first supported in Capture One 10.1.2, you can install those style packs in Capture One 10.1.2 or newer versions of the software.