Yes, you can. You have access to over 2000 questions in your CrunchPrep course, and you can choose to practice questions of any type and any difficulty level.
The quiz section in the CrunchPrep course has very advanced filters which you can apply and select only the hardest questions. For example, if you wish to solve the hardest geometry questions in our bank, you can apply the relevant filters and do so.
CrunchPrep gives you the flexibility to choose whether you wish to practice a particular set of difficulty levels, or you wish to start a practice session that is adaptive, much like the GRE exam.