In theory all information should be remembered but realistically this isn't possible. I am yet to start my ATPL but from what I understand, once you have covered all the material the QBs serve as a good guide on the type of questions and their wording.
The amount of hours you spend a day will depend on how fast you want to get it done. Some people have gotten it done in as little as 4 months spending 6-7 hours a day while others spend 2 hours a day to get it done in 12 months.