Yes, you can control the volume from the phone using the phone's volume buttons just like we do in case of any other headphones.
No. Airpods do not have storage space for media.
Yes, many people does that to improve the battery life.While using only one AirPod at a time, your iPhone will switch over to a mono mixdown so, you can hear both sides of any stereo.
Yes, you can use Apple Airpods with any Samsung mobile phone, which has Bluetooth 4.0 or higher connectivity option.
Look past their offbeat design and you'll find that Apple AirPods' compact size and high convenience factor are a winning combination.