The key will say "for Beta Testing".

It is not beta, it is a full product. Pre-release keys will say that.

https://www.steamgifts.com/discussion/omWHd/free-deiland-pocket-planet-if-you-own-the-original-deiland-check-your-mail

Also please, allow deletion of giveaway. If key does not work.

Thanks and Good Luck.