Completed means to have all the necessary parts or elements and lack nothing.

Finished means it’s over and done with.

Done means finished or fully baked.

Eventually, development will stop on a project, and everything around the project will slowly continue to move and change.

When software development stops, the project begins to rot.

It could be a new operating system release.

It could be a new programming language release or paradigm shift.

It could be a new framework release that has a security update.

It could be a third-party library on which your project depends.

It could be a drive fills up from database records or logs overflowing it.

It could be the machine the software runs on that gets powered off, and no one notices.

People could stop using the project because it is no longer needed.

Maybe no one understands how to keep the program running.

Eventually, the project will stop running because we turn it off or no longer understand how to keep it running.