CAT is essentially an exam being conducted on behalf of IIMs and for IIMs. Yes, other 165 institutes also consider CAT score mainly hence, this phenomenon makes CAT, the most coveted and sought after exam.
CAT has been going through many changes for the last couple of years but an even standardization has been maintained.
Most of the aspirants take other exams to test water of their efficiency before they appear in CAT.
CAT is an exam on accuracy and speed. Your analytical skills will be on anvil.
Be ready for the challenge as CAT will be conducted in coming October which is just nearing everyday and for serious aspirant like you time is in fact fleeting so stay informed and inspired.