Could you give a full summary of the story of Kaka Mahajani's friend who was against idol worship and his experiences in Shirdi?

Certainly. Chapter 35 recounts the story of a friend of Kaka Mahajani who was a devotee of the formless and averse to idol worship. He agreed to visit Shirdi out of curiosity but made his friend promise he wouldn't have to bow or give Dakshina. Upon arriving at the mosque, Sai Baba immediately addressed him in a tone that perfectly mimicked the friend's deceased father. This profound experience caused the friend to forget his resolve and bow at Baba's feet. Later, Baba twice asked for Dakshina, but only from Kaka Mahajani, pointedly ignoring the friend. This exclusion, contrary to his original vow, left the friend feeling restless, showing how Baba had completely overturned his initial skepticism and awakened a desire for connection.