Yes. If your hotspot is listed as a choice in Wi-Fi networks, you can use it as an access point.

The A1-MR supports lossless playback of CD quality audio, with zero compression. While you can play higher than CD quality audio to the A1-MR through DLNA, UPnP, or high res streaming apps like TIDAL and Qobuz, all audio is transmitted at 16-bit 44.1kHz.

Yes. You can play music from your computer library or NAS.

Yes, anybody connected to the same network can control volume and the music source.

The A1-MR is a 2.4GHz device but most networks are dual-band, so select 2.4GHz during A1-MR setup. 2.4GHz has more range, meaning more places you can place your system. 

Sending music to multiple A1-MRs can be done with any source after grouping the systems together. Start by playing music on one through the app, Airplay, or Spotify Connect. Then in the app, drag any additional systems onto the system that is playing. They will synchronize and you will be able to control the volume of every system separately. The app will remember these settings until they are changed.

You will not be able to synchronize music between the two systems, but both will show up as playback devices in Airplay or Spotify Connect.

You'll need to make sure you have gone through the initial set up process for the A1-MR before moving onto the below steps.

For iPhone users:

1. On the iPhone, swipe to open the Control Center. (the swipe direction is dependent upon the iPhone model you are using)
2. In the music control area, tap the AirPlay button.
3. A list of AirPlay capable devices seen by your iPhone will be shown. Tap the A1-MR to connect to it.
4. Once connected, you can use your iPhone to send audio to your A1-MR without the need to open the Audioengine Control App.

For Mac users:

Option 1:

1. Make sure that your Mac and A1-MR are on the same Wi-Fi network.
2. Go to Apple menu > System Preferences > Sound.
3. Under Output, you should see a list of any devices you are able to AirPlay to, and the A1-MR should be an option. If you named the A1-MR during setup, it may appear under that name.

Option 2:

1. Hold down the Option key on your keyboard, then click on the speaker icon in your menu bar. You will then see a list of audio output devices that are on your local network - select the A1-MR.
2. Once you change the audio output to an AirPlay device, all audio coming from your Mac will go through the A1-MR, and not the internal speakers on your Mac.
3. To change the audio output back to your Mac's internal speakers, you can either Option-click on the speaker icon again and select internal speakers, or go back into System Preferences and change it there.

Once you have set up all of your A1-MRs on your Wi-Fi network:

Open the Audioengine control app. Swipe from right to left in the app to the "Device" screen where your A1-MRs are listed. Determine which group of  A1-MRs you want to be your primary, then touch the "+" in the upper right corner. A list of any additional A1-MRs you want to add will appear and you can tap the empty circle to add a check to the bubble, then tap "Done" You can add multiple A1-MRs into that primary A1-MR for whole-home playback.

The A1-MR uses the ES9023 DAC. As the A1-MR uses your home wi-fi network, it is lossless and no compression is needed.

Sending audio to multiple A1-MR units at once will not impact the audio quality.

Any audio source can be used for multiroom playback through your A1-MR(s) when using AirPlay, or when streaming audio via DLNA / UPnP, or using the streaming services integrated into the Audioengine Control App. The A1-MR(s) need only first be configured into groups using the Audioengine Control App.

For music streamed through Audioengine Control App, or from streaming applications built into the Audioengine Control App, the A1-MR streams music directly over your Wi-Fi network. The stream will continue whether your device is taken out of range or turned off altogether.

Airplay, generally speaking, makes a connection between your source device and the A1-MR, through your network. If your device goes out of range of the network, or the application on your source that is playing audio is closed, playback will stop.