If we need overall CAT %ile, should we need also to clear sectional cut-off or without clear sectional cut-off overall CAT %ile consider??

Well,  sectional percentiles are decided looking into how well you have scored in that section as compared to the others. For instance, last year  a score of 62-65 would have fetched you 99+ percentile in VA-RC, however only a score of 33-35 in DI-LR would have given you 99+ percentile, this means that most of the students have actually scored well in VA-RC pushing the percentile high, whereas DI-LR being difficult, most of the students didn't score that high. So sectional cutoffs are actually decided upon your performance in that section. Now adding the scores of these three sections will give you an aggregate score and an overall percentile will be decided solely on the basis of that aggregate score, not based upon the percentiles of the other sections.
There have been cases when students have scored an aggregate percentile of 90+ but have miserably scored a percentile of just 60+ in one of the sections. This is because they scored well below 90 percentile in one section but their scores of the other two sections balanced that lower score, boosting their overall percentile.
Now this was how percentiles are given.
Almost all the IIMs declare sectional cutoffs and give calls considering sectional percentiles too but there are a few colleges which do not pay much heed to sectional cutoffs like IRMA, MICA, IIM A-FABM, IIM Ranchi, etc.
Prepare well for GD-WAT-PI.
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All the best!!