Upgrading to the premium version of the app unlocks a host of awesome features and benefits. One of the most impactful features is the Build Your Own Quiz study mode, a step-by-step custom exam creator that puts you in control of what you study. You can find the Exam Builder in the Study tab, under Study Modes.
There are multiple different filtering choices within the Build Your Own Quiz feature. Those filters include:
Questions from specific subject areas
Unanswered or new questions
Missed or incorrect questions
Total number of questions to be quizzed on
Choosing between showing the correct answers as you go or at the end