[Closed] Google Home and T Music playing on different devices

So, I've built up a wee collection of Google Hubs and speakers - picking them up when Google have a sale on and they are set up in a single Google Home account (account covers 2 houses - or 2 different wifi networks) - 4 speakers, 2 hubs and a chromecast. Overall account has links to my various media solutions - YouTube Music being my music player - just moved to Premium a few days ago, to get rid of all the adverts.

Anyway, latest device was added yesterday and added to my Google Home account without any issues. However, when it plays music, it does adverts as well and tells me I should upgrade to Premium for a tenner a month (which I'm already on) - doesn't do it on the other devices.

If someone else asks Google to play music on a different device, the device that is currently playing music stops - so it seems I can't have the music playing on multiple devices at the same time - is this correct?

What needs to be done to allow me to play music on the speakers/hub without stopping play on any other device? This seems like a really major pitfall to the system if it only allows playback on 1 device at a time.

Also, anyway of getting it to only play my uploaded music library? I've tried loads but it refuses to use any of the music in my library that is uploaded to YT and it only plays from YT 'store' itself rather than my files.

Cheers.