According to the Satcharitra, should a Guru's teachings to one person be kept secret from others?

No, Chapter 18 explicitly refutes the idea that a Guru's instructions should be kept secret. The text describes this notion as 'merely imaginary and a meaningless fuss.' To support this, the author states that even teachings received in dreams are shared for the enlightenment of all. As concrete proof, Chapter 18 cites the example of the sage Budhakaushika, who narrated his dream-vision of the Ram Raksha initiation to everyone, demonstrating the principle of sharing spiritual wisdom openly.