Duolingo VI from EN versions:

Trees:
v0: 2015-01-07, ?  (Beta)
v1: 2016-04-21, ?  (Beta)
v2: 2016-10-10, 75 Skills (75 Different Lessons)
v3: 2018-12-20, 84 Skills (84 Different Lessons)

Paths:
1.0: 2022-09-10, 75 Skills (75 Different Lessons) (49 units)
2.0: 2023-08-06, 84 Skills (84 Different Lessons) (54 units)
1.1: 2023-09-10, 75 Skills (75 Different Lessons) (48 units)
2.1: ?, 84 Skills (84 Different Lessons) (? units)
1.2: 2024-05-01, 75 Skills (75 Different Lessons) (85 units)
2.2: 2024-05-01, 84 Skills (84 Different Lessons) (CC units)

tree_vi_en_v1_experiment
tree_vi_en_v2_experiment
tree_vi_en_v3_launch_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.