what are the key tops for passing f5

There are no 'key topics' - all of the syllabus is important - even more so now with the introduction of multiple choice questions. There is no alternative but to study everything (by watching all of the free lectures on here and practicing using a Revision Kit from one of the approved publishers).

Thank you for the reply but is their a must topics that always come in the exam in section B

Really? Maybe you should look at past exams and realise that you are wrong!

Mr Moffat but that was a question if there is a must questions that comes always? was trying to find out from u.Thanks for your time to reply to my messages will surely take your advice to check the past paper.

There is no topic that comes always - sorry!