Does Chapter 18 support the idea that a Guru's instructions should be kept secret? Please explain.

No, Chapter 18 directly refutes the idea that a Guru's teachings should be kept secret. The author calls this notion a "merely imaginary and a meaningless fuss." The chapter advocates for the open sharing of spiritual wisdom for the benefit of all, stating that even instructions received in dreams should be told for everyone's enlightenment. To prove this point, Chapter 18 cites the example of the sage Budhakaushika, who shared the dream-vision of his Ram Raksha initiation with everyone. The chapter concludes this argument by comparing the Guru to monsoon clouds, showering the water of self-bliss universally.