There is a touch control panel at the top of the soundbar itself (Power, Volume, Input, Bluetooth). Press and hold the power button for 5/10 seconds to force a reset / restart. When it boots up, you can change the inputs directly on the device.
in 8 out of 10 cases: stereo. surround massively emphasises the upper frequencies and leads to an unsatisfactory sound image despite a very nice spatial effect. (for details see my comment)
Yes, it works without problem. If you want to connect a TV box and another device to the sound bar, I advise you to order a HDMI mutliplug with a swtich (cheap on "wish" websites...)