Tamil Nadu Open University

Yes, you are eligible to apply. Thee eligibility depends on the type of course that you wish to pursue, the details of some courses are stated below:
Diploma: Class 10th cleared from a recognized board with minimum 40% marks.
Bachelors degree: Class 12th examination with at least 50% marks.
PG Degree: Bachelors degree from a recognized university with at least 45% marks.

Hello Laxmi,
I have actually not understood. You were able to complete your BA based on 10th? If yes, then what's the need for doing 12th now? But if you have obtained degree from UGC approved university, then of course it remains valid.

The eligibility depends on the type of course that you wish to pursue, the details of some courses are stated below:
Diploma: Class 10th pass from a recognised board with a minimum of 40% marks.
Bachelor's degree: Class 10+2 examination with at least 50% marks.
Post-graduation degree: Bachelor's degree from a recognised university with at least 45% marks.
Graduate & PG programs may also require you to appear for the entrance exams such as NCHMCT, AIMA UGAT, eCHAT, etc.