Hiragana not in the right order
I just started the Japanese Beta course, but sometimes it's asking me words or hiragana that i have never been introduced before. For examply it asks me a hiragana from lesson 4/5 instead of from lesson 2/5. The same happens with words. It just starts asking me what is summer, without ever showing it to me.
Welcome to Duolingo =) Partly this is the way Duo works, some words are introduced with images first, others are just tested and you'll have to use the tooltips to figure out their meaning. On the other hand there's the strange algorithm which chooses the vocabulary for a lesson. When strengthening (basic) skills I also get words and sentences from more advanced skills (not only with Japanese btw)... really weird
I have started working on my Japanese with duolingo but found it to be a little confusing. My advice is go out there and study the alphabets first then come back and work through the Japanese language here.