I'm currently on Dolphin 7.1.6 and want to upgrade to 7.2.1 - what instructions do I need to follow? - I'm getting the impression I first need to upgrade to 7.2.0, and then upgrade to 7.2.1?
Yes you need to upgrade first to 7.2. Check everything if all modules are running well after the upgrade. Once everything is in place then you upgrade to 7.2.1