Sony MBH20 has average talk time of up to 8 hours. So, you can use it for almost 2 days talk time.
Yes, you can use Sony MBH20 with Gionee A1 easily.
Yes, You shall receive USB Cable for the same as part of the standard packaging.
Yes, you can.
No. You cannot change the battery of Sony MBH20. Sony MBH20 comes with in-built battery.