Do we need to remember what google service is for what function ( The whole product list)?

Yes and no :).

Each GCP exam will target on a specific set of key services, so for sure if you’re on a particular exam you won’t need to remember all of them in-details, but you need to do so for those services related to your exam. For the rest of services that are not "the key" in your exam, it’s kinda enough if you have an idea (just a short idea) of what it it about.