Buying Premium Pass in Just Dace 2017 also works for 2018 edition?
Solution 1:
Every new copy of recent Just Dance games comes with 3 months or 1 year (console editions with a golden cover) of Just Dance Unlimited aka premium membership.
The membership is per game (if you got one in 2017 you need a new one on 2018).
The Just Dance 2017 songs are in the 2018 edition with Unlimited. Since Just Dance 1 every game has it's own set of songs with few exceptions but you can play them in the recent editions with the subscription.
The better is to get 2018 and use the 3 months/1 year of unlimited and start paying after that (most songs on a single game).