How to deploy one app engine app to multiple projects

Question

My problem is that I want to create dev, stage, prod environments by using different GCP projects.

Basically they are running

Answer 1

The "standard" approach is to use versions, e.g.

qa.myApp.appspot.com

Once a version is ready for next step, you deploy it with a different version id.

One problem with using multiple projects is that you have to maintain a different data set for each project.