Short answers, pulled from the story.
The Iwakura Mission had three goals: to gain recognition for the newly reinstated Meiji imperial dynasty, to begin preliminary renegotiation of the unequal treaties with Western powers, and to study Western industrial, political, military, and educational systems. The treaty renegotiation failed, but the comprehensive study of Western institutions provided a blueprint for Japan's modernization.
The Iwakura Mission departed Yokohama on the 23rd of December 1871 and returned on the 13th of September 1873, lasting nearly two years. The original itinerary was extended by almost four months due to unsuccessful treaty negotiations.
The mission was led by Iwakura Tomomi as extraordinary and plenipotentiary ambassador. His four vice-ambassadors included Okubo Toshimichi, Kido Takayoshi, and Ito Hirobumi, all of whom were also ministers in the Japanese government.
Tsuda Umeko joined the Iwakura Mission as a student at six years old and was left in the United States to complete her education. She returned to Japan in 1882 and in 1900 founded the Joshi Eigaku Juku, which is now Tsuda University.
The mission visited the United States, the United Kingdom, France, Belgium, the Netherlands, Prussia, Denmark, Sweden, Austria, Italy, and Switzerland. On the return voyage the delegation also stopped in Egypt, Aden, Ceylon, Singapore, Saigon, Hong Kong, and Shanghai.
The mission was first proposed by Guido Verbeck, a Dutch missionary and engineer working in Japan. He drew in part on the model of the Grand Embassy of Peter I as a precedent for sending senior statesmen abroad to study foreign institutions.