Yes and No. If you have an active data package then you could use that or your personal wifi.
You can use Spotify, IHeartRadio, Pandora, and such over a 3G or LTE network, but it'll eat up your data.
iHeartradio is 100% Free. Its ad supported however.
Some of the stations are live. You can set up a custom station as well on iHeartradio.
Yes you need WiFi
You need Wifi to do anything on YouTube.
Yes, you need wifi to FaceTime.
Yes you do need wifi
You only need WiFi if you are downloading new books. Books already downloaded do not need wifi
No.
WiFi usb adapter is a WiFi card.
No wifi
You need a wifi router or a Nintendo wifi usb