In which two use cases should a Python virtual environment be used?

When developing multiple Python projects in the same environment that have the same Python package version requirements.

When developing multiple Python projects in the same environment that have conflicting Python package versions.

When developing the same Python application across multiple systems using the same application requirements.

When creating a new project with several development environments in a multi-project development system across the infrastructure.

When creating a new project that has a clean development environment in a multi-project development system.