Yes, Sony NS-WS623 does have NFC connectivity option.
Yes, Sony NS-WS623 is meant for the rough usage and it is both - waterproof and dustproof.
Hold down the button 1 for 3 seconds.
You will hear the startup sound.
When the Walkman turns on, the lamp (2) lights up.
Hold down the button (1) for 3 seconds.
You will hear the shutdown sound. Then, the Walkman and the lamp ( 2 ) will turn off.
Yes, it does have fast charging. Charge it for just 3 minutes and it will work for another 60 minutes.