Yes you are eligible if you satisfy the following mentioned below criteria:

1. You must have completed your graduation in Bachelor of Science Botany honours with at least 50% marks in the aggregate of the examinations of graduation.
2. There is no age restriction for taking Banaras Hindu University postgraduate entrance test. You can apply at any age for Banaras Hindu University postgraduate entrance test.

Read more about Banaras Hindu University postgraduate entrance test by clicking on mentioned below link:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.careers360.com/exams/bhu-pet/amp&ved=2ahUKEwjWq8Xz6cv1AhWQTGwGHVAhCecQFnoECAgQAQ&usg=AOvVaw2CegSij8jYi1a-A2RQhwSl