Best application/way to cover this requirement (Randomized test creation) ?

Quick question, can you confirm what you mean by "along with their propositions (hidding the valid ones)"

Are you looking to randomly produce 30 questions from a list of say 100 questions and display the question and all 5 propositions and the user has to select the correct proposition?

If so then I would create a hidden sheet with 7 columns in as follows:
A - The question
B through to F the Propositions (one per column)
G the number of the correct answer eg if the correct proposition for Q1 was in column B then it would be 1, column F would be 5 etc

For the purpose of this example we'll assume theres 100 questions in your "bank"

1. I would have VBA code to loop 30 times, each time selecting a random number between 1 and 100,
2. you'll then need to check that the number hadnt already been picked, you could do this by either adding new numbers into an array or marking an additional column with an indicator to show the question has been chosen already. So you loop through those items to see if any match this question number, if so, you pick another random number and do it all again until you get one that hasnt been picked.
3. Copy the details of that row into your "question" sheet (minus column G of course), include in there the row number of the question.

That will set up your questionnaire.

To run the questionnaire theres a number of different ways you can do it, for example have the user enter the number of the correct answer into a later column of the question or (as I prefer) have them click the cell and use an On_Click event to register which cell was chosen (this can then put the relevant column number into a hidden cell as if theyd typed it in)

have a "Completed" button that when clicked checks each of the values in that column against the relevant row in the Questions sheet to see if the two answers match and output the score.