How to know which questions to skip in RD

So I have given my PT test and decided that ncert is not enough for me and so I have bought Rd Sharma book (class 10) Any idea how to know which questions are important without wasting a ton of time redoing ncert level questions.

My reason for doing this book is for tough questions so can I ensure that I am not wasting my time doing easy ones.

Only do the HOTS or will I be missing something if I skip all the LOTS and basic questions?