What happens if OCI (Overseas Citizenship of India) is not renewed? [migrated]

I read contradictory information.

1) OCI lasts all life. AGAIN-

2) OCI must be renewed each time the passport is renewed before 21 January.

3) The holder of the OCI card can go to India with OCI with his old passport without renewing it. enter the description of the link here

Now, if a person under 21 lives in India and has OCI on his old foreign passport, his foreign passport is renewed but does not renew OCI. Is this person's stay in India legal or not?