What codding skills it requires and how much time does it take?
Or how much does it cost?
difficult question to answer, given spotify has both a desktop version and mobile apps (for ios and android). If you want all 3 (desktop, ios and android) its going to be more expensive of course.
however, spotify is a terrible example. If you want to legally offer a streaming service, you need to negotiate with artist (or companies representing artists) how much you are going to pay the artist, before you can offer there music in your program.
actually someone asked this question:
https://www.quora.com/How-much-does-it-cost-to-make-an-app-like-Spotify
So its certainly expensive. The skill required also depends heavily on the features as mentioned in the quora answer
For sure, it’s still difficult and expensive, as it’s connected with copyrights and dealing with greedy music producers.
So, you can check here for more info and be ready for challenges.
Thank you all for your suggestions:)