Duolingo ID from EN versions:

Trees:
v0: 2015-12-02  ? (Beta)
v0: 2018-08-15  ? (Beta)
v1: 2018-08-15, 69 Skills (Different lessons)

Paths:
1.0: 2022-09-10, 69 Different lessons (44 units)
1.1: 2023-09-10, 69 Different lessons (45 units)
1.2: 2024-05-01, 69 Different Lessons) (79 units)

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.