1) Conventional TYS (Ten Year Series) assessment book contain
all questions from the past years. Usually the most common one is
categorized by Year. This one means you're
actually looking at the actual questions that came
out from the previous years.
There's also another type of 'tys' which is categorized by
chapter/topics. For this one, the first few questions of each topic
are usually crafted by the publisher.
Applies to biology, chemistry, physics,
2) If you're refering to the 'unique' questions; questions that
are really crafted with lots of creativity juice, these are very
few like 5 to 20% of each paper. Such questions test on your
understanding of a particular topic.
3) For MCQ, close to 50% of the questions are similar to the
past years questions. When you do a lot of MCQ, you will notice a
lot of similar occurance.