Class 12-science

After 12th you can get into research field, you can aim to get into IISERs (Bhopal, Trivandrum and Pune). To get into these institutes you need to clear IIT-JEE.

NEET is the entrance taken by government for admission in medical field especially MBBS and also BAMS and BHMS. PCB student have many chances like B.Pharma, B.Sc and many more.

Advanced Diploma in Pre-Production and Game Design
Advanced Diploma in VFX
Aircraft Maintenance Engineering
B.E (Mechanical Engineering)
B.Sc. (Biotechnology)
B.Sc. Applied Physical Science
B.Sc. Life Sciences.
B.Tech (Aerospace Engineering)
B.Tech (Mechanical & Automation Engg.)
BAMS
B.Arch
Environmental Studies (KRVIA),
BCA (Bachelor in Computer Applications)

As you have mentioned that you have taken your Diploma. Yes, you can pursue B.Tech in civil engineering through lateral entry. You can get direct admission in 2nd year of B.Tech through lateral entry.

Hi Daljit,
Different programmes and universities have different entry requirements and criteria. Ideally you must have a first class , majority of them asks for more than 75%. You must also take the IELTS, an overall score of 6 is recommended.

You need to clear the entrance exam to get into graduation college for engineering. It depends on your field of interest which course you want to pursue in future.

Yes, you can do a Diploma in radiology after 12th.

If you really want to pursue your career in aviation and will be satisfied with your life if you get a chance in it, then do it rather than regretting the whole life that you didn't achieve what you really wanted. But as you have lost the basics of maths, focus on it more and join a good coaching or better hire a good maths private tutor so that you will face no difficulties while practicing it.But you have also mentioned regarding your interests in biology. So be wise in making your decision. See what interests you more and will make you happy.

Graduates and post graduate in the field of psychology have several interesting opportunities in counselling and special education teaching. You may refer to following article for career details as a psychologist: https://www.shiksha.com/medicine-health-sciences/paramedical/articles/popular-careers-in-psychology-for-the-best-minds-blogId-3626.
You may opt for BA (Hons) psychology after 10+2.