Sony MBH20 comes with Sony battery only. As per company, it offers up to 100 hours of standby time and about 7 hours of talk time.
Just about 8 grams.
Yes, you can use Sony MBH20 to hear music also.
No. Sony MBH20 do not have volume control button. You cannot increase or decrease call volume but you can use your mobile phone's call volume control button for the same.
It takes about 1-2 hours to fully charge Sony MBH20.