Hello Prakash

You can appear for biology exam from National institute of open schooling.

You will have to pass biology exam as an additional subject. Uou must make sure to obtain minimum 50 % marks ( physics + chemistry + biology )

After qualifying this exam you will be eligible to qppear for neet.

Neet eligibility criteria-
The candidate should be an Indian.  The candidate must have completed 17 years of age. There is no upper age limit.

The candidate must obtain minimum 50% marks in physics, chemistry and biology . English language is also mandatory.

To know more kindly refer the following link.

https://medicine.careers360.com/articles/neet-eligibility-criteria

For neet preparations you may go for neet packages

https://learn.careers360.com/knockout-neet-may/