MCA

Getting a good job depends on your skills and profile. Yes, college matters for the sake of learning and placement, but a good student will get a good job even if he or she studied in a small college. Also, if you are planning to do BCA then checkout other equivalent courses like B.Sc, IT/CS.
All the best.

Hello Asish,
There are several colleges admission procedure for MCA is direct admission after any graduation. But, top colleges conducts its own entrance examination or accept state level entrance examination score like TANCET, KMAT, PUCET, etc.
All the best for your future.

Yes, on that basis of CET you can take admission in MCA
K.J Somaiya College.

Yes, you can start a computer training institute. You need to set up the institute. You can take help of PM's Mudra Scheme too. All the best.

Admission to MCA is not given without any entrance exam. You can check out some private colleges like Amity or Sikkim Manipal. They might have separate admission process.
Government colleges will give admission only if you have given entrance.

You should try to get in only for MCA degree. Dual degree will be waste of time and money as you are already Bachelors. If there is no such course available for MCA, then try for any other college.
All the best.