With the current implementation, it's not possible to finish a Quiz with sequential navigation early in the app.

In the LMS, it is possible to use the "Finish attempt..." button at any moment, thus allowing long quizzes to be submitted even with unanswered (and even unvisited) questions.

The app, however, doesn't allow it and the "Finish attempt..." button is only enabled in the last page of the quiz. This happens because without obtaining the information for all the questions, it's not possible to submit a quiz (otherwise, the summary and review lack question information and show an "unsupported question type" error message).