CAT

As per my experience I don't think that an year gap affects for CAT preparation adversely affects your chances of getting admission in any institute in IIMs or any other institute of India. The entire interview process is meant to gauge the students on their knowledge, skills and attitudes as well as their inclination of doing a MBA program.
If you are dropping out of your current job for one year there should be a justification as to what were the reason for opting out of your job. There are various examples of students who have scored a hundred percentile while working and thus the interviewers always discuss the reasons for dropping out. But, if you are able to justify it well and convince them about yourself. I personally don't think that it would negatively affect your chances into IIMs or any other institute of India.

MAH-CET is a state-level management entrance exam. The exam is conducted by the Directorate of Technical Education, Maharashtra, for admission to various management courses such as MMS, PGDBM, and PGDM in various institutes in the state of Maharashtra. There are many institutes in Maharashtra which accepts only CET score.
Check the below link for the list of colleges –
https://www.shiksha.com/mba/ranking/top-mba-colleges-in-india-accepting-mhcet/2-2-0-0-9247
Similarly, you will find other state common entrance tests. Colleges in respective state accepting those scores -
https://www.shiksha.com/mba/articles/20-mba-entrance-exams-you-can-take-this-year-blogId-11473
Karnataka PGCET - https://www.shiksha.com/mba/exams/karnataka-pgcet
Kerala - KMAT - https://www.shiksha.com/mba/exams/kmat-kerala
MPMET - https://www.shiksha.com/mba/exams/mpmet

Tomorrow is too late, yesterday is over and now is the exact right time to start! CAT aspirants, it is very important to allocate enough time while preparing to the basic section. Here are a few tips to crack this exam in the first attempt.
1.The foremost thing that you need to choose is whether to go for coaching or to take self preparation. If you have decided to prepare by own take the help of a consultant.
2.Go through the syllabus thoroughly and start preparation from basics, after clearing with basic part you will be able to understand the rest of the part clearly. Get all the information related to CAT Exam.
3.To check your knowledge on basic part, start attempting the mock tests which you can find on the Internet and try to focus on weaker sections and practice well.
4.To know the important sections analyse and know the previously asked question papers and we advise you to read news papers, magazines daily to improve the vocabulary.
5.To crack CAT exam in first attempt, the candidate should focus on accuracy as there will be negative marking for wrong answer. While locking the answer correctly read the question twice or thrice.
6.To crack the CAT exam in the first attempt, the candidate should work hard to lessen the problems rising before the exam. This CAT exam is all about mental state, the depleted mind cant help to answer the logical questions.
6.After the complete preparation, take daily the mock tests for practice and time management. This helps to crack the CAT exam in first attempt.
All the best!