Yes, Sony MBH20 does have call ending button also.
Yes, You can use Sony MBH20 with Nokia 3310.
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.
Yes, you can use Sony MBH20 with Gionee A1 easily.
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.