First of all, the third level (finale) of talking about 100 questions is definitely good.

If you have plenty of time and want to sprint full marks, you can buy them together at the second level (the core question), which is the best.

One hundred questions are classic, and each question has a detailed explanation.

In contrast, most of the questions in the finale are very detailed, but many of them only have answers, and there are no steps, which is embarrassing. Moreover, some questions are really too difficult. I think no one can take such a difficult question. It is better to pass all of them.