The Tips and Notes for the course are not currently available in the apps. But you can access them by using a desktop or mobile browser. Click on the Skill you're interested in. If T&N exist for that skill, you'll see a light bulb icon; click that and you'll see the notes. Currently T&N exist primarily for the earlier skills in the course.
So far, I understand that interrogative and assertive can be differed by the question mark in written, and by intonation when we speak. Sometimes, in spoken utterances the intonation goes flat, I mean not like typical questionning tone which goes up. But then our speaking partner would confirm if it is or it is not, 'ano' or 'ne'.