1) Yes, it runs Android so it will (The ZX300 really was not much of a disaster as you think)
2) Don't know as it's not officially out, but there might not be
3) Play Store is supported so APKs shouldn't be necessary
Again, why can't you just get an Android phone? If you're only going to use this with Bluetooth headphones it's not worth spending over $800 on this, which is only wasting your money even more. Even then I'm confident you'll find some sort of issue with this player. I've been trying to suggest this to you for the 5th time now but you just refuse to listen, even though there's no real purpose in getting a device like this based on your use case