'Poem Fiasco' - steps 12th and 13th

Link to the project - https://www.codecademy.com/paths/web-development/tracks/learn-git/modules/learn-git-git-backtracking-u/projects/poem-fiasco

In step 9, it was written that I need to make some changes in all the files. According to the project, the changes should be undone at the end of the project. But, that didn’t happen.

I did everything as it was said steps 12th and 13th. But, after all the steps, when I wrote git log in the terminal, the commit that I wrote in step 11 (the most recent commit) was still there. I think I did something wrong in the last two steps, due to which the changes in step 9 can’t be undone. I need help to understand what went wrong.