Reference:
Project resources are components that are necessary for successful project implementation. They include people, equipment, money, time, knowledge - basically, anything that you may require from the project planning to the project delivery phases.

The recommended approach is to have folders corresponding to teams/departments and they manage the projects within that.
-> Sharing a single project will cause a conflict of resources, billing, concerns, etc.
-> One folder per project is unnecessary overuse of abstraction/grouping.
-> Teams and projects in a company should ideally be centrally managed in a single Organization.

Instance is alive for no more than 24 hours, Can be pre-empted with a 30 second notice, Discounted Significantly.
Preemptible VM is an instance that you can create and run at a lower cost than normal instances.
However, Compute Engine might stop (pre-empt) these instances if it requires access to those resources for other tasks. Preemptible instances are excess Compute Engine capacity, so their availability varies with usage.
Live at most 24 hours Can be pre-empted with a 30 second notification via API and are Discounted significantly Reference link- https://cloud.google.com/compute/docs/instances/preemptible

After the service provider provisions your connection, you can start passing traffic between your networks by using the service provider's network.

Firebase/Firestore is easy to build and is suitable for user information that could bvary in nature.