There are different types of "detail" questions. Some of them truly refer to a specific information in the passage. e.g., who did what? what a word refer to? In my experience, these can be "easily" looked up in the passge. (I use quote, because it's not that easy especially when the passage is long and involves a unfamiliar topic). THere are also the "inference" type of detail question. For those, a good understanding of the passage is needed.
I have seen several posts here saying that on the CAT, there are only 3-4 Q/passages (whereas in OG, 7-8 Q/passage), and most of the Q are not "detail" questions. Perhaps those who have taken the test can elaborate as to which type of "detail" questions you have seen on the CAT?