You cannot change the battery of this headset.
Yes, Samsung HM1350 comes with volume control buttons.
No. It does not have Active Noise Cancellation.
No. Samsung HM1350 does not have an auto answer function.
To connect Samsung HM1350 with your smartphone, please follow the below steps.
01) Make sure that your smartphone's Bluetooth is switched ON.
02) Switch ON your Samsung HM1350
03) Now search for the visible devices on your smartphone
04) select Samsung HM1350
and you're done.