Suppose I find a question in CAT difficult and I skip it .Is is still possible for me to get 90% above marks even if I skip the questions.

Yes it is absolutely possible. In fact CAT is all about this. How well you strategize in those three hours. CAT is an aptitude test that tests how smartly you answer the questions. What I mean by smart answering is how aptly you chose the right questions among the given set. You never have to answer all these questions, because anyway when you answer all the questions, you might attract negative penalties.
So it's better you skip few questions that you are not certain about, chose the questions whose answers you are sure of and never waste time in questions that take a lot of time.
CAT is mainly focusing on what you can do in the least amount of time, not what can be solved but takes a lot of time.
Anyway, attempting around 50+ questions overall, on an average with almost 100% accuracy will most likely, fetch you a percentile of 90 above (as per previous years trends)
All the best!!