Go backwards in levels?
I started Spanish with duolingo a couple days ago... I did a few years of Spanish in High School (like 10 years ago) so I understand some very basics... I took the test to skip the super basic stuff and it put me in level 4. I'm now at level 6 and just took my first quiz. The quiz covered A LOT of words I don't remember and haven't covered yet in my practice... I think the program let me skip too far ahead... is there a good way to go back to a lower level and review what I "tested out of" ??
The progress test covers skills from the whole course and not just the stuff covered by the user. Hence, there's always new stuff until the whole tree is complete.
Regarding checking out already completed part, you can click on a completed skill and then practice the whole skill (strengthen) or redo individual lessons.
The purpose of the progress quiz is to show your progress over time. It covers the entire course and allows you, when you take the test more than once, to see how much progress you've made. You would have encountered a lot of words and grammatical forms that you hadn't covered yet, even if you'd taken the first three lessons.