Yes, you can create actions locally and then upload them to GitHub.com
Yes, you can test them on a dev branch on GitHub.com
You can treat GitHub Actions the same way you would treat your code. Feel free to add it to a dev branch and then merge it to your default branch afterwards.
Hi Anthony!!! Happy to answer these questions.
Here's a reference on how to build your first workflow: dev.to/github/github-actions-build...