Wordpress Quiz Purchase plugin

I have a website in which I need following things to be done: For quiz i have 2 plugins in mind (option b is very close to my requirement and option a is free available) a. [login to view URL] b. [login to view URL] What needs to be done: 1. Candidates can purchase subscription based test (only true / False questions) and can download certificate (custom Certificate) 2. There would be package where students are going to subscribe(weekly/Monthly/or anything) choose the test they want rather purchase specific test For example : if somebody purchase A package(10 test), students can only avail 10 quiz's ( any 10 of them out of whatever number of quizzes available) and each test have specific certificate which he/she can download from dashboard anytime (no matter what his subscriptions is, the limitation is on 'quiz in specified time') and if he/she purchase B package - then limitaion is on number of tests(specified in package B) and duration of availability of the quiz (specified in B package) So we can create any number of packages