Duolingo DA from EN versions:

Trees:
v0: 2014-06-04  ? (Beta)
v0: 2014-08-25, ? (Beta)
v1: 2015-02-03, 70 skills (70 Different Lessons)
v2: ?
v3: 2016-03-15, 62 skills (62 Different Lessons)

Paths:
1.0: 2022-09-10, 70 Skills (70 Different lessons) (45 units)
2.0: 2023-01-02, 62 Skills (62 Different lessons) (40 units)
1.1: 2023-09-10, 70 Skills (70 Different lessons) (47 units)
2.1: 2023-10-14, 62 Skills (62 Different lessons) (41 units)
2.1: 2024-05-01, 62 Skills (62 Different lessons) (71 units)

tree_da_en_v1_experiment
tree_da_en_v2_experiment
tree_da_en_v3_experiment

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.