A:AnswerIf you are talking about the Walkie Talkie feature, I know that series 4 & 5 have it. However, you and your party (that you are trying to connect to) must both have Apple Watches. Don't rely on it too much though. It's not consistent.
A:AnswerNo. While you can use a cellular Apple Watch while using an Android phone, the watch won't pair to the phone, so they won't exchange data. You would also need an iPhone to setup the watch.
A:AnswerTo use the cellular option of the watch you need to have a “service” with your carrier to utilize it so you would have to open another “line” on your account but that’s if you want to use cellular.