Google CloudPlatform remove/delete app deployed during tutorial steps
Yes, disabling an application prevents charges, but only from the App Engine prospective, there could still be other changes from other Cloud products usage. From Disabling an application:


  Your app's resources in both the standard and flexible environment are
  disabled and therefore, won't incur charges. However, billing charges
  can still occur for the other services in your Cloud Platform project,
  for example you can still incur storage charges for your stored data.


To completely end all Cloud billing for a project you can shut it down (i.e. mark it for deletion!). But please note that you won't be able to re-use its ID, ever.