Welcome to GMAT Club!
1. You have a high goal but it is not laughable. It is possible to improve 200 points within 3-4 months. 200 points requires a good and rigorous jolt. For example,
variantguy https://gmatclub.com/forum/12-weeks-to- ... 97343.html was able to get to 750 and he is 30, so you can definitely get to 720. Many prep companies advertise average improvement from in-person courses at 120 points (that's what our research shows from GMAT Club Reviews based on
MGMAT and Veritas Prep courses). Private Tutoring can that average to 160.
2. I did not use any of those as I was super poor, so I studied with books but I made sure that created notes for each topic and if I made a mistake, I made a promise never to make a similar mistake again and to explore the material behind that mistake and make sure I am prepared. I started at 540 and went to 750.
3. You can do it but you will have to restructure your days (read varintguy's debrief and replies later for how many hours per day he studied).
4. YOU DO NOT NEED TO TAKE CATS/TESTS UNTIL YOU COVERED ALL QUANT OR ALL VERBAL. What's the point? You will get some questions right but if you have not covered geometry and statistics, you will bomb those, so your score will inconclusive and you would have wasted a test, bunch of time, and probably discourage yourself. Instead take small quizzes after/within each chapter and aim to have 90% right to hit your score. If you are not getting 90% right (under timed conditions - always time yourself doing any question and make sure you are done in 2 mins - you must feel the pressure of the time). Anyway. if you are not hitting 90%, think why, and find a solution.
5. Focus on material instead of questions. Some people feel that if they do 1 hour of learning and then 2-3 hours of questions per day, that will help. It does not. Questions check your ability/knowledge. They are a measuring tool. You don't want to spend 3 hours measuring something and only 1 hour of actual work.
MGMAT Guides are great!!! Make sure you also have the Official Guide. The latest edition would be the best but if you already have an earlier edition, that will do too.
6. Your are older and your options for MBA will be different than if you were 27. Make sure you know your options (EU programs, EMBA, PGPX in India, and some specialty ones such as Sloan and Stanford MSx). US Top 20 FT MBA won't take 35 yo applicants. Let me know if this is news.
7. You have a bachelor's degree I assume? No matter your accomplishments, pretty much all programs will ding applicants without a 4-year degree. Make sure you research that aspect if you are unsure about your undergrad.
Again welcome and hopefully all my warnings have not scared you off. That was not my goal