In case you want to re-do \ practice the whole unit that you've made Legendary here is how :
- Start the lesson just before the unit trophy
- Note the link in the address bar; example: ***duolingo.com/lesson/unit/1/level/4
- Pay attention to the last number
- Modify the link by increasing the last number by 1; example: ***.duolingo.com/lesson/unit/1/level/5
- Hit Enter
Now you can re-do this unit legendary challenge