Bug: How to access any skill.
I found a bug in the course (I don't know if it works with every course), where you can access any skill i.e. you could go to Future right from the start. All you do is change whatever skill you're on to the one you want to go to e.g. change https://www.duolingo.com/skill/hv/Basics-2 to https://www.duolingo.com/skill/hv/Future and you'll have access to the future skill. I hope that made sense.