Hey Domenico,
Essentially, you can take as many CATs as you would like although that may not be the best decision.
You take the CATs in sets of six. During your first six CAT exams, you'll receive unique questions pulled from our question bank. If you complete all six tests and would like to do more, simply call or email us and we can reset your CATs. Your previously answered questions will be released back into the question bank and you will start a new set of six tests. However, this means that once you reset, you will start to see some repeat questions.
As far as the Question Banks, each Bank contains 25 practice problems that you can answer as many times as you would like.
When you're ready to access your online resources, simply register your books here:
http://www.manhattangmat.com/access.cfmBest,
Matt Mapplebeck
Student Services Associate
Manhattan GMAT