Duolingo HW from EN versions:

Trees:
v0: 2018-06-15  ? (Beta)
v1: 2018-10-05, 13 Skills (13 Different Lessons) (Beta)
v2: 2019-04-18, 23 Skills (23 Different Lessons) (Beta)
v3: ? (Beta)
v4: 2020-02-20, 30 Skills (30 Different Lessons)
v5: 2021-02-28, 38 Skills (38 Different Lessons)
v6-v7: ?

Paths:
1.0: 2022-09-10, 38 Skills (38 Different Lessons) (24 units)
2.0: 2023-02-20, 51 Skills (51 Different Lessons) (33 units)
1.1: 2023-09-10, 38 Skills (38 Different Lessons) (25 units)
3.0: 2023-11-05, 52 Skills (52 Different Lessons) (34 units)
3.1: 2024-05-01, 52 Skills (52 Different Lessons) (59 units)

tree_hw_en_v1_experiment
tree_hw_en_v2_experiment
tree_hw_en_v3_experiment
tree_hw_en_v4_experiment
tree_hw_en_v5_experiment
tree_hw_en_v6_experiment
tree_hw_en_v7_experiment
tree_hw_en_intro_section3_existing
tree_hw_en_intro_section3_new

https://liuch.github.io/duolingo_courses_overview/
https://duolingo.fandom.com/wiki/Course_list
https://duolingodata.com/
https://duolingodata.com/oldtable.html
https://ardslot.com/duolingocrowns.html

Edited by Mat!/Ozone, 2024-05-02.