I have an iPhone 5 - I usually listen to Amazon Prime music. Is it possible to use music control feature on Vivoactive to control music on Amazon Prime?
No work-arounds. Whether you accept it is a personal decision. You can choose to accept it, or ditch Garmin, or ditch Amazon Prime, or ditch the iPhone†, or find something you use in conjunction with all of the above (meaning you wear your Garmin, bring your iPhone, and have that other something on you as well when you work out) to give you the functional outcome of controlling music without interacting with your handset.
† The Garmin device user can control other than the native music app on an Android mobile device.
I use BT headphones, which control any active music player on iOS. Personally, I use Google Play Music. For me, this is the most efficient solution when recording an activity. I don't need to exit the activity, scroll to the music control widget...
As of update 3.40, I am now able to control the Amazon music app through the Garmin watch widget. It will even start the app for me if it's not running, which is great. I've got an Android 7.0 Phone. Works perfectly! :)