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 remote control.
Hold down the button 1 for 3 seconds.
You will hear the startup sound.
When the Walkman turns on, the lamp (2) lights up.
Yes, you can connect it with phone and talk and can use as a normal Bluetooth headset.
No. Sony NS-WS623 does not have FM radio.