I recently upgraded to Spotify premium to solve the problem that I have that Spotify technically don’t allow to stream from Sonos multiroom system and a mobile device at same time. I get the same problem when streaming from the car (tesla). I'm not streaming the same playlist or song. I see that spotify in general should handle more than on stream but looks like there are some limitations here.
So now I've faked up 2 new accounts for myself for the car, the sonos multiroom system and my mobile. The next problem is that I don't want different playlists on my devices. I want my playlists on all the accounts. I can to some extent understand that you can't get them exported automatically, but it should be possible to send them to other users. This is where everything fails. In Spotify you can only send via facebook and I don’t have 3 facebook accounts, and I dont use facebook as log in on any of these..
I've moved your post to Help - Other as it's not a bug 🙂
Unfortunately, you can only stream on one device at a time.
You can go around that and set your mobile device offline ( you will need to make your content available offline ), this way you will be able to stream at both your Sonos speakers/Tesla and mobile device.
To set your mobile device offline go to "Your Music", click the gear icon in the upper right and select "Offline mode" under Playback.
As for the second question you can share playlist using the direct link: