CBSE 12th

Dear Vishwa,
What is the objective of you doing a short-term course in Hotel Management after 5 years? What did you do in last 5 years? Which place you are from? I have no clues to these questions.
Still, you can do short-term course in Hotel Management. But, if you are looking for a career in HM, I will advise you to do a proper 3-4 year Degree in Hotel Management.

On the basis of marking scheme, Madhya Pradesh Board is tougher than CBSE.
Madhya Pradesh Board has some advantages like they give 4 set of expected question papers from where most of the question comes from every year (Parikshabodh or Parikshaaadhyan). And, CBSE post some sets of question paper and they are little handful, but not very much.
But, CBSE have syllabus advantage because many good entrance examination (i.e, JEE Mains) follow CBSE books.

On the basis of marking scheme, Madhya Pradesh Board is tougher than CBSE.
Madhya Pradesh Board has some advantages like they give 4 set of expected question papers from where most of the question comes from every year (Parikshabodh or Parikshaaadhyan). And, CBSE post some sets of question paper and they are little handful, but not very much.
But, CBSE have syllabus advantage because many good entrance examination (i.e, JEE Mains) follow CBSE books.

1. For Maths student, IIT (JEE-ADVANCE) is a common entrance examination after qualifying. Students can get into IIT or NIT or many good colleges of India. Important thing is exam though. And, IIT and NIT have excellent placement cell where you can get great jobs.
2. Do whatever you really want to do is always an option where you can become expertise and be on top in on your own field.

You can choose any of them, because both are extremely good departments.
Choosing biology can make you a doctor, researcher etc.
Choosing Computer science can land you working in Major companies.
If you can study a lot and mug up everything go for biology.
If you can continue coding or debugging for hours or want to develop app, software or have serious interest in computer science, then only option it.

Yes, you are eligible. Those who are appearing for 12th board exams can apply for NCHM JEE 2018. Application forms are available in the nchm.gov.nic website.