Bang, both versions of Cheap Thrills, and both versions of Sorry are indeed in Just Dance Unlimited accessed from Just Dance 2018.
In fact, almost of the 2017 dances are already included in Unlimited. (Early this year, they also put in almost all of the 2016 dances. Same Old Love is about the only song currently missing from 2016. The one year where they really need to add more songs is 2015, which is missing Black Widow, Dark Horse, both versions of Diamonds, What Does the Fox Say, Problem, Love Me Again, Me and My Broken Heart, and more. Funny that most of the 2014, 2016, and 2017 dances are included, but 2015 has several missing.)
Anyway, they were very generous including most of the 2017 dances with Unlimited right off the bat with the 2018 launch. (Thank you, Ubisoft!)