Question 1
The environments that should have a two-way deployment connection in
this scenario are Test Sandbox and Production Org.
Which requirement needs to be met to perform a quick deployment for
change sets or Metadata API components without testing the full
deployment?
To perform a quick deployment for change sets or Metadata API components without testing the full deployment, it is required that each class and trigger that was previously deployed is covered by at least 75% joint test coverage. This ensures that the majority of the code being deployed has been sufficiently tested to maintain functionality and stability in the production environment. Reference: Salesforce Deployment Considerations