Yes, Google cloud tokens are unique. Tokens are nothing but an ID, or registration token issued by Google cloud messaging servers to the client apps. Because only having that will help you in receiving messages. Google cloud messaging has been deprecated 2 years back in 2018, and it has been replaced with Firebase cloud messaging (FCM).
If you are a beginner in the Google cloud platform and wish to get certified in it, then I would suggest you check out the Google cloud certification from Intellipaat, which offers you industry standard instructor-led training with dedicated time for project-work and exercises. Also, have a look at the YouTube video made by Intellipaat experts to help you get started.