I'm posting this to this selected forum so more registered users can read (or translate) it than those with only a good command in the English language in the "I speak English" forum category and who may not read into that sub forum regularly.
I came across this post on Reddit:
A user explains in this interesting post what can potentially happen to your tree progress on the old app version if a course gets a major update while it was made for the path and how that update might negatively reset your tree progress to a specific point if they don't match.
In a post it was mentioned for the Japanese course and latest (Non-Kanji) changes and therefore referenced.
The Portuguese from English course is currently safe so I'm heavily using the old grammar and verb tense heavy 91 skill tree designed by former volunteer contributors.
Another course is the French from German course with 129 skills.
Similar classic volunteer structure.
Layout might have something in common with French tree3 from the former volunteer EN->FR team.
Both contain dedicated verb tense skills so it's a pleasure to be able to jump to the bottom in my PT course (last 1/3, starting at the second half) and just to focus on leveling up more advanced past verb tenses, (Future/Conditional) Perfect, 4 Subjunctive skills, etc.
I might have luck too with the PT->FR course.
Not every Duolingo course changes a lot or gets restructured heavily from the bottom up.
So if you want to stick to the old tree and an older Android app version make sure that you don't sign up for a course which is well-known for multiple past changes and where future changes are quite soon expected.
Hope this helps.
Best regards from Germany