Sony WS623 has 4GB internal memory and you can further expand it up to 16GB with the help of MicroSD card.
No. It does not have.
Yes, it does have fast charging. Charge it for just 3 minutes and it will work for another 60 minutes.
No. Sony NS-WS623 does not have FM radio.
No. Sony WS623 comes with non-removable battery.