Android: Quell has all the same levels as Quell+, but contains adverts. Quell Memento has no adverts, but only a limited amount of levels, with the option to buy the remaining chapters in-game, while Quell Memento+ has all the levels. There is currently no Quell Reflect on Android.
iOS: There are currently no free versions, so essentially all the games are the + version.
Questions
Quell has all the same levels as Quell+, but contains adverts.
Quell Memento has no adverts, but only a limited amount of levels, with the option to buy the remaining chapters in-game, while Quell Memento+ has all the levels.
There is currently no Quell Reflect on Android.
iOS:
There are currently no free versions, so essentially all the games are the + version.