Class 12-science

Engineering is one of the sought after career by Science students.
Architecture.
Merchant Navy.
Commercial Pilot.
Bachelor of Science.
National Defense Services-Indian Navy Officer, Indian Air Force.
Railway Apprentice Exam.
Business Administration and Management Studies.

After 12th Science, you can do B.Sc, B.Tech/B.E, medical, etc. You can also go into management, or banking. If you are interested in computers, you can do one of the following:
B.Tech/ BE in computer Science
B.Tech/ B.E. In information technology
B.Tech/ B.E in electronics and telecommunications
B.Sc in CS
B.Sc in IT
BCA.

You are a PCM student, so you should definitely go for engineering. And which engineering you should choose depends upon your interest and skills in the respective subjects and topics.

Yes, then also you can enter into good engineering colleges by giving their Individual Entrance Test. Some examples may be VIT Vellore, SRM Chennai.

Hi Sandipan,
As per current scenario and considering Future scope fields, Data analyst, Game developer, IT professional, Management in top ten B school. If you are good at lab analyzing skill and demanding for high pay scale, go for Oil and gas industry with petroleum engineering/management. If you are well versed in Maths and number crunching, go for Investment banking. Pursue B.Com CA. Remember there is no issue, as you are non-commerce student. All the Best for your future.

You can prepare for civil services via coaching classes or online classes. On the other hand, you can do it by yourself using different books available in the market for preparation of SSC. You should do your graduation simultaneously along with your preparations.

Last year, rules were changed. Now, rank depend on JEE score.

After 12th you can go for various streams like BBA/B.Com, /B.Sc/B.E.-B.Tech. You can also go for integrated BBA-MBA course or integrated B.Tech-M.Tech. 75% is not at all a less score. You can choose a stream of your interest. You must work hard and perform well in graduation.

Your percentage is too low to take admission for this course.
For admission to the course, candidates need to have qualified 10+2 from a recognized educational Board with a minimum aggregate score of 50% with Physics, Chemistry, and Biology as main subjects.
If it happen recently, then you can go for improvement exam (every board gives a time period of minimum 2 years to improve your marks once).And continue your preparation for your respective career option simultaneously.

If you have a valid reason, it's completely fine. You just don't need to give up. It is no shame to fail, just come back stronger next time, when you get the chance. If you do well in your graduation, I don't think it would be an issue. All the best.