What were the main Upanishads that Maharaj gave discourses on during his sittings?

The provided text from Chapter 0 explicitly states that Maharaj did not give discourses on the Upanishads or openly explain profound Vedanta subjects. His advice was primarily ethical, aimed at purifying a disciple's character before introducing deeper knowledge. The text explains that his verbal counsel consisted of general ethical principles, often delivered through stories during his three daily sittings, which addressed matters on the minds of the people present. Therefore, there is no list of Upanishads he lectured on, as this was not his method of teaching according to the source.