You can check the charging status with the lamp ( 3 ).
While the battery is charging: orange when charging is complete: green
Yes, you can connect it with phone and talk and can use as a normal Bluetooth headset.
Yes, it does have fast charging. Charge it for just 3 minutes and it will work for another 60 minutes.
Sony WS623 has 4GB internal memory and you can further expand it up to 16GB with the help of MicroSD card.
Yes, Sony NS-WS623 is meant for the rough usage and it is both - waterproof and dustproof.