Some limitations due to the way Spotify API works:
You need spotify premium to be able to play the songs via their API.
You can browse the playlists, songs etc without the premium though.
You need an active device with spotify logged in. This means you need to open up spotify app in your desktop or phone & play-pause some song to make it active. The device will lose the active status in some time if you do not interact with either it, or this clone for a while.
The clone does not include all the functionalities of the actual spotify web client.