Am allowed to skip lessons in Spanish
Lessons opening up without prerequisites done.
This happened to me. I reported it to support and was told
"It seems as though the skills you mentioned unlocked because you had previously learned some of the words that were introduced in those skills."
Seems strange to me regardless of what words I've learnt because I haven't completed the requirements for those skills. However, Duo is aware of it and think it's normal.
I've had the same happen to me in the german tree before.
Today when I completed the (german) science lesson/skill and unlocked Verbs Reflexive, I also got Business 1, Language and Verbs: Present 3 as well. So I got three more unlocked than I should have.
Business 1 and Verbs: Present 3 each had one lesson within them completed when they were unlocked.