Keshab Chandra Sen was a notable Indian social reformer and religious leader who lived in the late 19th century. He was associated with the establishment of the Indian Reform Association, which was founded in 1870 with the aim of promoting social and religious reforms in India.

The Calcutta Unitarian Committee was established in 1850 by a group of liberal-minded individuals in Calcutta (now Kolkata), including Raja Ram Mohan Roy and Debendranath Tagore. The Committee was formed to promote the ideas of Unitarianism in India, which emphasized the oneness of God and the unity of all religions.

The Tabernacle of New Dispensation was a religious organization founded by Keshab Chandra Sen in 1866. The organization was based on the principles of Brahmoism, which emphasized the worship of one God and the rejection of caste and idol worship.

Based on this information, it can be concluded that Keshab Chandra Sen was associated with the establishment of both the Indian Reform Association and the Tabernacle of New Dispensation. Therefore, option 2: "2 and 3 only" is the correct answer.

It is worth noting that although Keshab Chandra Sen was not directly involved in the establishment of the Calcutta Unitarian Committee, he was greatly influenced by the ideas of Raja Ram Mohan Roy and other members of the Committee. Sen was also instrumental in the formation of the Brahmo Samaj, another religious organization that promoted the ideals of Unitarianism and sought to reform Indian society.