Can I use my app subscription on the website, and vice versa?

Yes, you can now share your subscription between devices. If you subscribe on the website then you can use the same subscription on the IOS or Android app, if you sign in using the same credentials. You can also use your Apple or Play store subscription on the website if you are registered and have signed in on the app at least once after subscribing, and are then signed in on the website. Any playlists that you create will also be shared between devices that you are signed in on.