how to create a playgroundbook in mac swiftplayground ?

Download the Xcode11.1 project from https://developer.apple.com/download/more/?=Swift%20Playgrounds%20Author%20Template .Build it on Xcode 11.1 and drag your .playground book in the products folder into Finder. Upload the .playgroundbook file.

I learnt from this ,

https://www.freecodecamp.org/news/how-to-make-something-with-swift-playgrounds-33e560b84184/

Are we allowed to use 11.1? Since the T&C of this challenge explicitly mentioned that 11.4 should be used ...

11.4.1, actually.

If you are creating .playground for Xcode Playground, you need to use Xcode 11.4.1.

Are you going to create a .playgroundbook or a .playground ?

Isn't a .playgroundbook automatically created when you start a new playground in the Swift Playgrounds app?

You can create a playground book on Xcode 11.1 and then export the .playground book. You are allowed to submit the .playgroundbook as long as it works on Swift Playgrounds 3.3