A:AnswerNo. The sub plugs into the wall for power and must be connected through your Wi-Fi to link to an appropriate Sonos product. There is an input for a wired Ethernet cable connection and an HDMI cable input to connect to the Arc or eARC connection on your TV.
A:AnswerThe button is for joining (pairing) your subwoofer with the soundbar. The subwoofer powers on without having to press a button.
https://www.sonos.com/en-us/guides/sub
A:AnswerI think you mean a Sub Gen 3. You can pair this sub with a Sub Gen 3 with the appropriate Sonos soundbar. If you meant a Beam Gen 2, yes you can pair this sub with it. There is no Beam Gen 3 at this time. Gen 2 is the latest Beam.
A:AnswerYes you'll need wifi or connection to your cell phone providers network that is if you do not have it hard wired. I do believe if your system is hard wired then it may still work if your wifi is down. I've yet to try this but will and maybe I can help further with this question.