Well, religion can be changed in India, but a caste can’t. A person born in upper-class caste can’t avail of the benefits reserved for SC/ST or OBC. One acquires caste by birth. Yes, if there is an error due to many circumstances, you can get it corrected. The following information states about the caste conversion from SC to General.
All in all, caste is still not autonomous and it is not a person’s own decision. It can be changed in special circumstances, if your parents belong to different castes, you have a choice of one of their castes. Caste change can be achieved legally only when someone has been adopted. And if a child (born in an inter-caste marriage) when attains the age of 21 chooses to vote for another caste of the father or mother in specific circumstances.
In the case of marriage, it is not legally possible to change from Scheduled Caste (SC) to Other Backward Classes (OBC) or religion, as instructed by the Supreme Court.
In a judgement, the Apex Court of India ruled that the caste is decided as per the kin of birth. It can not be changed through marriage. If a woman of general caste marries a man who is from scheduled caste, no matter what the ritual says, she can not change her caste legally and avail the benefits available to SC. Similarly, men also can not change their caste through marriage.