How do i memorize all the essays that could come up on the exam?

The method of memorization has to be done via you figuring out a way to commit information to your memory, whether that be via writing them out repeatedly, condensing the essay into main points which you can memorize and therefore expand on or by bullet pointing each topics main points and memorizing through association the relevant theories and research. Practise is key and fundamental to being able to memorize all the required information.