I have backlogs and gaps of many years in my academic history, what are my chances with top companies?

If you have been out of school for a while taking more courses may show that you are current in your field, and more education is always beneficial. It may be a good idea to figure a better way to explain your education gaps and backlogs other than procrastination and laziness. Those are not virtues to a prospective employer. Pursuing personal interest and travel may appear more acceptable if you can explain what you did with the time. Often applicants just say personal reasons with no explanation for the gaps. I don't recommend that approach as it leaves the it wide open for the employer to imagine a reasons which may be worse than procrastination. You have certificates from prestigious institutions so you should have no problem getting interviews. I would not initiate discussing the gaps and leave it to the interviewer. If asked I would explain in the positive terms what I did with the time. Good Luck The PracticaL Mentor