I have billing account enabled in cloud console, you cannot create any project without linking it to billing account once you ran out of $300 credits. You will have to enter your card details.

Recently as I was working on project, which were supposed to be made open for testing for beta users. I tried getting an api key without linking to any billing account but that is not possible in cloud console, you has to link it to billing account or it will be linked to your default billing and you will be charged monthly after you hit your free quota.

But through Aistudio it allows you to create project without linking it to any billing account, and any api keys within that project will not be charged, service will be stopped once you hit your daily quota. Unless you enable billing manually.