MBA/PGDM

If possible take admission in a college where dual specialisation is offered. Otherwise choose marketing.

Yes, but you still have scope if you do it from a reputed place. Also, if you enhance your skills side by side, you will do well.

Continue with your field with MLT. Though MBA is well paying but you will have to entirety step into a different game. Your degree will be of nil value. If you are very much interested in MBA then go for healthcare management. Otherwise continue with MLT.

You can do so if you have an urge of entering into the corporate world. But doing MBA will totally lead you to whole new world of management besides of technical world. If you are in love with your technical field then, doing anything in your technical field you can achieve more what you seeking by doing MBA.
Do what you really want to do. If you really want to go into the management field then you must go but think once why have you done engineering if you really want to do management then. Think twice before act. You one decision can change your whole life.

It is simply impossible to get admission into a top-ranked college for a full time MBA program without appearing for any entrance exam(s), clearing the necessary cutoffs and performing well in the interview rounds (if shortlisted for it).

Hello,
A gap taken for MBA exams preparations is quite common nowadays, so it's not really an issue. However, one should make the most of this gap time by utilizing it for other activities like certification courses, internships, social work, etc. These activities will ensure you edge over the other freshers (in terms of the resume) and also highlight your interest in past academics and/or future MBA stream. A gap taken solely for the exam preparations might create a negative impact on the interviewers, as these exams generally require 3-4 hours daily.

Hello,
Yes, one can pursue MBA in India with or without any kind of work-experience. Though not a compulsion, it is always beneficial to pursue MBA with some prior experience (preferably 2 years).

Hi,
According to your back ground I would suggest you to take marketing and operations as specialisation in MBA. B.Tech people are genuinely preferred for operations and your experience in sales will help you to find a better room in marketing.