I am making a text game for a class project, and the easiest way for me to submit it is to publish the game and submit the link. However, I want to be able to go back into the game and edit it to make it longer/better than what I have so far so I can add it to a portfolio and submit it again for a later project.
When I publish a game, can I still go to it and edit it? Or What is another way I can submit the project without publishing it so that my teacher can still play the game?

You can still edit a published game. Changes won't be made live, so you can test out different things, and then just click "publish" again to update the public version.