Jeba, there is no upper age limit for NEET. If you have secured a minimum aggregate of 50% in Physics, Chemistry and Biology, you are eligible for NEET. It is 50% for General Category, 45% for PWD and 40% for OBC,SC,ST. Though you are a Post graduate, because the basic eligibility criteria for appearing in NEET is 12th, only 12th aggregate is considered.

if you have had atleast 2 subjects among Physics, Chemistry and Biology in your Bachelor's degree, your code will be 06. Code 06 says: B.Sc. Examination of an Indian University provided that he/she has passed the B.Sc. Examination with not less than two of the subjects Physics, Chemistry, Biology (Botany, Zoology)/Biotechnology and further that he/ she has passed the earlier qualifying examination with Physics, Chemistry, Biology and English. This is the most apt code for you.

For registration, use the link: https://ntaneet.nic.in/Ntaneet/Registration/NewReg.aspx . You can check the complete application process at our page, https://medicine.careers360.com/articles/neet-application-form.