Doesn't necessarily have to be a quiz.
Set each step up as a separate activity - could be a quiz, but I would probably use an assignment submission (using online text) - works well for group submissions too.
Then use conditional release for the next step - based on activity completion for the previous step. Activity completion could be based on achieving a certain grade, or just based on you (teacher) confirming its been done/complete.
With an assignment submission, if its not good enough, you can reopen it/revert it to draft with whatever feedback you have given the group to improve it.