This is also one of my complaints about Duolingo to be honest, in that they only give you information about the lessons you're doing if you navigate to a specific page before starting an exercise (on the web interface, I haven't used the mobile interface). Ui-bug for Ui-bug compatibility?

My first thought too, I was trying to type in the "tip" box before I found the code tab

It could be on purpose? I've found that I learn better when I am forced to read ALL the instructions and then try to solve the problem without having quick access to the instructions.