Chemistry Spl

Yes, you certainly can reappear for 12th Class exams. Or you could pursue a Diploma on the basis of 10th class. Pursuing a Diploma will be easier than 12th and it is also considered equivalent to 12th. But I would suggest passing the 12th in the failed exam. Diploma is 3 years long and 12th can be completed in a year. But see what you can manage and then decide accordingly.

Ewing Christian College is the best option to pursue M.Sc. After that, you can go for Allahabad University main campus or CMP PG college.

It is not advisable to do CA after opting for PCMB in 12th standard, if you insist to do, please enrol with ICAI with CA-CPT and ensure to get a good coaching institution. Pursue a degree course through distance, it will be very helpful for.

Here is the link of respective colleges providing Masters in forensic science:
https://www.shiksha.com/science/colleges/m-sc-forensic-science-colleges-india
Amity is also a good option for this course but obviously it's costly. You can check whether they consider Bachelor in chemistry marks for admission in Masters at respective colleges' website.

B.Sc in Chemistry would be best, if you want to go for Lectureship. You can also go for lectureship through Biochemistry, if you want. There is no foundation on restriction on the career choice after B.Sc. Both will be good for lectureship and biochemistry.

Yes, you will be able to apply after 2 years for M.Sc. You may be asked to produce an affidavit stating your reason for gap, but that can be easily managed.

Some very good job-oriented courses are B.Sc in Chemistry, Botany, Zoology, or bachelors in nursing, physiotherapy or bio-medical. Bachelors in biotechnology, genetics and bioinformatics are also good and wide options.