Safely Upgrading or Rolling Back Ceylon: Practical Steps and Verification

When you upgrade or downgrade a Ceylon installation, you need to consider its modular distribution layout, platform dependencies, and the fact that the official repository is archived. What are the recommended steps to perform a safe upgrade (or rollback) of a Ceylon installation, including:

• Prerequisites (Java version, system compatibility)
• Downloading and installing the new release
• Verifying the installation (module resolution, compiler functionality)
• Rolling back to a previous version if something fails

How can you ensure that the upgrade is performed without breaking existing modules, and what verification steps should you include before and after the change?