The options allow you to check which JLPT you are learning, so that the vocabulary list and the games adapt themselves to your level.
You can also filter the vocabulary list by JLPT if you are learning more than one at the time, or by keyword being either in the kanjis, the hiraganas or the english meaning.
You can test yourself using the quizz, two mini-games or the reading training, which are in this order in a growing difficulty.
The reading training will need you to have the japanese input. Shouldn't you have it, please download the Google Japanese Input at: https://play.google.com/store/apps/details?id=com.google.android.inputmethod.japanese&hl=fr
Good luck in learning Japanese!