Hello,
A2DP can be installed and tested here: [Deprecated] [TESTING] Bluetooth audio streaming (A2DP). We’ve made it clear that Bluetooth audio streaming is experimental and will continue to be so for the next couple of months.
Regarding the dongle, you can return it per our money back guarantee, but keep in mind that it’s the recommended dongle for audio streaming. When we do achieve a stable release for this, you will want to be using that dongle 
Sam