CBSE 10th

You have to score good marks in graduation and entrance exam to get admission
You should have 50% in SSC and HSC

Aishwarya, for a job in Google and Facebook you first need to get a degree. And academic record somewhere does matter as big companies often look for consistent record.
Join some university where companies like Google, Facebook etc come for campus placement and you academic record doesn't hamper your chance of sitting for placement of Google, Facebook etc.

MBA can have more scope and job opportunities.
All the best

Hello Vinay,
No it won't hurt your placements. You have nearly 3 years of work experience and that would help you to cover up your low academic scores. The companies will then focus on how well you did during these 3 years. Also, not all companies focus on academic scores.

After 10th, Please join for HSc with PCB / PCBM combination. Prepare for various medical entrances like AIMS, All India Medical, Defense Academy, State entrance etc. along with your HSc studies.
As a first step of this, find out the best entrance coaching centre in your location and take admission. Many institutions are providing full time residential entrance coaching along with HSc Science group.
All the Best

If your aim is Government job you can continue with B.Sc. You will able to complete your graduation in 2 years and will be eligible for majority of Government jobs where eligibility is graduation degree. If you change to engineering now, you will require 4 years to graduate.

Ankur as per your profile admission in the good courses is quite difficult but you can go with M.A. journalism, economics, social work, PGDCA . These are good course with job orientation

Not really
You can justify yourself in the interview that why you have low scores. You should carry a genuine and acceptable reason for that.

I am not sure regarding that as it is the matter of ACPC. I suggest you to call ACPC help centers for more details.