As a Free user, you won't be able to play music on demand.
Pick and play on mobile is available only for Premium users. However, it's available on selected playlists for Free users as well, there will be no shuffle symbol next to the title of the playlist. That means, you can choose a song you want to play form that playlist and you have unlimited skips.
You can still play on demand using e.g. desktop, even without Premium Subscription.
If you wan't to see the comparison of different Premium plans offered by Spotify, make sure to check outthis support article.
More detail on how Spotify Free works on mobile can be found here.
Hope this shed some light!
Emilia_8Rock Star 9
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