Questions about Audioengine B1

I don't know. If the Bluetooth version of the Air-pod - whatever that is ;) - is correct, then it should work. It works great with IPhone.

If you have paired your mobile phone with the Audioengine, you can adjust the volume via your mobile phone.

Where should I know this from....

I disconnected the power for a little more than 1min. The unit starts up without any further action and works without any problems when connected.

Es ist Bluetooth 5.0

Yes, also works with mobile phone charging cable (micro-usb)

Yes, if your active speakers have RCA inputs it works right out of the box without additional accessories.

Yes, https://audioengineusa.com/shop/adapters/b1-bluetooth-music-receiver/ But the reception is a bit weak...

Yes. It supports both RCA phono and optical inputs on an AVR. The optical input on the vsx2020k is limited to only the TV/DVR/VID channels though so if you would want optical connection you need to use one of them.

Unfortunately we only deliver to Switzerland and Liechtenstein. We ask for your understanding.