Yes, it does have call receive button.
Yes, You shall receive USB Cable for the same as part of the standard packaging.
Yes, you can use Sony MBH20 with Gionee A1 easily.
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.
No. Sony MBH20 do not have FM radio.