Downloading workflow artifacts
You can download archived artifacts before they automatically expire.
Who can use this feature?
People who are signed into GitHub and have read access to a repository can download workflow artifacts.
Reference:
https://docs.github.com/en/actions/how-tos/manage-workflow-runs/download-workflow-artifacts

GitHub Actions allows you to configure environment protection rules, where you can require specific users or teams to approve the deployment before the workflow proceeds to the next step. This ensures that the required reviewers approve the workflow before any sensitive actions (such as deployment) occur.

[D] GitHub Actions now supports a concurrency key at both the workflow and job level that will ensure that only a single run or job is in progress.
concurrency
Use concurrency to ensure that only a single job or workflow using the same concurrency group will run at a time.
Example: Using concurrency and the default behavior
The default behavior of GitHub Actions is to allow multiple jobs or workflow runs to run concurrently. The concurrency keyword allows you to control the concurrency of workflow runs.
Reference:
https://github.blog/changelog/2021-04-19-github-actions-limit-workflow-run-or-job-concurrency/
https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#concurrency
https://github.com/marketplace/actions/actions-mutex

The correct option is on: pull_request: branches: - release. This configuration runs only when a pull request targets the release branch and it does not run on push events.
The pull_request event triggers on pull request activity and the branches filter matches the base branch of the pull request. By specifying the release branch, this configuration limits runs to pull requests that target that branch. Because it listens only for the pull_request event, pushes will not trigger the workflow.

Reusable workflows versus composite actions
Reusable workflows and composite actions both help you avoid duplicating workflow content.
Whereas reusable workflows allow you to reuse an entire workflow, with multiple jobs and steps, composite actions combine multiple steps that you can then run within a job step, just like any other action.
A composite action allows you to bundle multiple steps into a single reusable action within a workflow. It is composed of multiple run steps or other actions and can be reused across workflows, making it the perfect choice for bundling a series of steps.
Reference:
https://docs.github.com/en/actions/concepts/workflows-and-actions/reusable-workflows