Make sure you read the whole of @AnotherElk 's link. It turns out that eventually the earphones worked on the FP2. And that is something that I can confirm myself from first-hand experience.
However, it seems to be “normal” that extra functionality like volume control and skipping tracks only works with the FP2’s pre-defined standard music app (I haven’t found a way yet to shift this functionality to my preferred app VLC) – but that is also the case with another headset I have been using previously.