Short answers, pulled from the story.
South Kasai declared secession on the 9th of August 1960, when Albert Kalonji, then in Katanga, proclaimed the region of south-eastern Kasai to be the Mining State of South Kasai. The secession followed Katanga's full break from the Congo on the 11th of July 1960.
Albert Kalonji was the founder and leader of South Kasai, serving as its president after the secession was declared. He had previously led the MNC-Kalonji faction of the Mouvement National Congolais and later declared himself Mulopwe, a royal title drawn from the pre-colonial Luba Empire, on the 16th of July 1961.
No foreign government ever officially recognised South Kasai. Belgium, South Africa, France, and the Central African Federation all provided various forms of support, but none granted diplomatic recognition. South Kasai maintained no diplomatic missions abroad.
Around 3,000 Baluba were killed in massacres carried out by Armée Nationale Congolaise and Katangese troops during the August-September 1960 offensive. More than 35,000 refugees fled to Élisabethville and as many as 100,000 sought shelter in Bakwanga. A subsequent famine and disease epidemic killed an estimated 200 people daily by December 1960.
South Kasai relied primarily on diamond exports, rerouted through Congo-Brazzaville after secession. The Belgian company Forminière was the state's principal commercial backer, receiving concessions in exchange for financial support. State revenue was estimated at thirty million dollars annually.
On the night of the 29th to the 30th of September 1962, military commanders led by Albert Kankolongo launched a coup in Bakwanga against the Kalonjist regime. Kalonji fled to Katanga and eventually to Spain. Central government troops arrived on the 5th of October 1962 to support the mutineers, marking the formal end of the secession.