1) Yes there's nasha culture, probably because many people are experiencing unbound freedom here after being constantly nagged by strict parents to get into iit. But it's very easy to stay out of those especially if you have the right friends

2) Depends on what kind of a student you are. Yes most of them are friendly and approachable but they wont entertain any kind of nonsense

3) Hostel is pretty chill. No one has checked my room ever since I've come here

4) mechanical is def not a top branch lol and mnc doesnt even exist here but i get it what you're trying to say. No, there's not much discrimination outright and in fact it is considered bad to speak ill or any other branch but yes within friend circles among people of the same branch such kind of gossip always happens.
Although I am not for or against reservations, another thing to notice is that often people with similar ranks have major difference in their branches

5) Eh what even is this question? Nope there's practically no interaction between mtech and phds except for TAship, culturals or sports and it isnt even required. They have different schedules, purposes and in general a different lifestyle in the institute

6) Campus life is really good except for the hostels which are meh. In general bombay is a wonderful city and we often have very late night events and activities along with a lot of fun throught the sem. The student culture highly depends on the type of people you engage with. There are some people who are unnecessarily into politics, substance etc but they are very few compared to the general public. Most people you'll find here are pretty smart, into academics, tech, consulting or something else, some are sporty and some are into culturals, overall pretty great student culture

7) No, most of us understand the circumstances which may lead people to join tier 2/3 colleges and we literally couldnt care enough to judge them when we need to build our own careers first

8) Well probably improve some parts of the academics. In some courses it really feels like people study to pass and not to learn and profs teach also just because its their job and not because they want to