Yes, you can use Apple Airpods with any Android mobile phones, which has at least Bluetooth 4.0 connectivity option.
No. Airpods do not have storage space for media.
The AirPods will begin charging as soon as they are in the charging case. It does not make any difference, whether the case lid is open or close.
When you take any of the AirPods from the ear, it automatically pauses the music.
You can also double-tap on the stem to invoke Siri, and ask it to play/pause the music.
Look past their offbeat design and you'll find that Apple AirPods' compact size and high convenience factor are a winning combination.