To completely remove the DB and start from scratch, go to the google console, on the left-hand nav, choose "Deployment Manager", and then look for your Neo4j deployment. Just delete the entire deployment. All of your VMs and setup will go away (so make sure you want to do this). Please note that the deployment leaves behind the GCP disks so you don't accidentally destroy data. If you want to 100% kill your cluster instance, then after deleting the deployment you should also go into GCP Compute -> Disks and delete the disks for the nodes, which will have the same names as the cluster nodes.
To stop the system service on the VM, use sudo systemctl stop neo4j. This will stop neo4j from running on the VM, but the VM will still be there.
More documentation on the VM specifically can be found here:
