Sony NS-WS623 is quite light weight. It weighs just about 32 grams.
No. Sony NS-WS623 does not have FM radio.
Yes, you can connect it with phone and talk and can use as a normal Bluetooth headset.
No. Sony WS623 comes with non-removable battery.
Hold down the button 1 for 3 seconds.
You will hear the startup sound.
When the Walkman turns on, the lamp (2) lights up.