B.Tech

Yes in some institutes and No in some institutes, it's possible to study M.Sc. In Physics after B.Tech in Mechanical Engineering. But only few colleges are giving chance for B.Tech students like Delhi University. Do some research about colleges giving this chance and join accordingly.
You would only be accepted to a few institutions if you wanted to pursue an MSc in physics. Traditional universities will not even accept you for a master's degree in physics. Furthermore, btech mechanical engineering is solely based on basic classical mechanics or lower level classical mechanics, the majority of which is newtonian mechanics.
BSc physics is focused on quantum mechanics, and almost all areas of study in BSc physics use quantum mechanics like there isn't any newtonian mechanics in the universe, so whatever they would be thinking in India about degree equivalence, a BSc physics is way higher than a btech mechanical engineering in terms of theoretical knowledge and depth of physics and mathematics, in fact, a BSc physics is way higher than btech, So, if you get into one of those select few universities, you'll have to work extremely hard or you'll end up in hell. Also, if you want to study physics overseas, a btech is ineligible for an MSc or MS in physics. Only those with a BSc/BS in physics are eligible. As a result, you won't be able to pursue an MSc in another country because their qualifying standards only allow for BSc/BS physics.

Hello Sayak Pal, it is very nice to see that you are interested in pursuing post-graduation in aerospace engineering. It is perfectly feasible and possible for you to achieve your goal. For this, you will need to appear for and clear the paper for aerospace engineering in the common entrance test for postgraduate studies in engineering called GATE. Here there are different papers for different subjects and a student is supposed to choose the subject in the which he or she wants to do post-graduation. For you are help and benefit I am attaching a link that will give you all the required information. I am sure if you study well, you can clear this examination and then complete yours are post-graduation in aerospace studies. https://www.shiksha.com/engineering/gate-exam
Best wishes to you.

You can do Masters in psychology being a B.Tech CSE graduate. It's quite easier to switch now to Masters psychology. Get ready to do hardwork since you are not a psychology background student. Few colleges won't allow non psychology background students, check before and join accordingly!
Without a bachelor's degree in psychology, you can pursue an MA or MSc in psychology. The eligibility requirements will differ from one university to the other. Many leading colleges provide an MA in Psychology to graduates with a 50 percent graduation rate. So, if you have a B.Tech with a grade point average of greater than 50%, you can apply.
Some colleges grant admission to courses based on their degree grades, while others grant admission based on their entrance exam rank. In addition to the written test, some universities will conduct an oral examination. Almost all major institutions offer this subject, which you may research on the university's website.

Hello Dumadiya! As you said that you completed your 12th standard in PCB, ( I. e; without mathematics) and preferring IT in Btech. The chances are less you get a admission.
But few institutes provide this opportunity by clearing their institute test which includes mathematics also. For example, LPU is providing LPU NEST entrance test, based on your marks and eligible criteria you will provided seat in respective branches.
On the other hand you are eligible for only few btech branches in some particular colleges. You are not allowed to join in NITs and IITs with PCB background because you are not allowed to give the JEE Mains and Advanced tests.
You will be eligible to do biotechnology in btech with PCB background in almost all the government institutions except NITs and IITs.
VIT Vellore, LPU Phagwara, SRM Chennai ,MIT Manipal, etc. are some of the best engineering colleges which are allowing PCB students in India.
Do proper research about the college and the courses it is providing and prepare for their tests and try to score best to join the branch you are preferring.

Yes, I'd like to let you know that, yes, you can apply to ordinary college after passing NIOS. It is a recognised board that holds the same weight as other boards. After completing your 12th grade at NIOS, you can apply to any of the colleges.
There are numerous colleges to which you can apply.you can get admission in any college for B.Tech being a NIOS board student. But you have to meet the expectations of the college requirements based on the score.
To pursue B.Tech from a reputable institute, candidates must meet all of the qualifying criteria listed below.
Students must have earned their 12th grade coursework in Science from a recognised Board.
Students must have completed qualifying courses in physics, chemistry, and mathematics.
At the qualifying level, students must have received a minimum of 50% in the abovementioned subjects and passing scores in the rest of the courses (varies from college to college)

Hello,
What happened that you are seeking a change of college in the sixth semester? The situation can arise when we feel suffocated in an institution and desire change. See theoretically it is possible. Just understand the different dynamics working. Your present college will not like to lose you since they may end up losing fees that you pay. The syllabus of your new college may not be compatible with your current syllabus. In view of all this, it's advisable not to break one's head over this issue. My advice is for you to continue in the same college if the situation is not alarming. But then if it's a must seek clarity on the procedure from the admin staff of your college. Best wishes to you.

Since you have not mentioned your caste, I am considering you as a general category student. Looking at the previous year WBJEE cut off, with 25 marks out of 200 in WBJEE you can accept a rank between 10,900 and 11,300. And considering this to be your general rank you have chance for government semi government or private colleges which include following college at the top: University of Kalyani. Haldia institute of technology. Feather please not that the above prediction is best on the previous year WBJEE cut off which match change this year as the WBJEE cut off bound to change every year and it depend on the various factors like: difficulty level of the, previous year cutoff trends, number of aspirants appearing, etc.