Manual deployment promotion + long lived preview deployments

Hello! I am working on a deployment pipeline and have a few questions:

1. Is there a way to promote preview deployments to production from a github actions?
- I would like to deploy a preview deployment, run my own smoke tests and then promote to production
2. How long do preview deployments last?
- Is there a scenario where one project needs to reference an older version of a different project?
- This is in an effort to combat api drift. I would like one projects to target a specific version of a different project

Thanks!