Short answers, pulled from the story.
The Republic of Mahabad was proclaimed on the 22nd of January 1946 and fell on the 15th of December 1946, lasting less than one year. Iranian forces entered Mahabad on that December date, closing its Kurdish printing press and banning the Kurdish language.
Qazi Muhammad led the Republic of Mahabad. He was the head of a family of religious jurists in Mahabad and had served as chairman of the Kurdish political party since before the republic was declared. He was hanged on the 31st of March 1947 on charges of treason.
The republic's relationship to the Soviet Union was contested. Qazi Muhammad acknowledged Soviet funding and supplies but denied that his party was communist, calling that characterization a lie by Iranian military authorities. Contemporaries including American diplomat Robert Rossow Jr. and historian William Linn Westermann branded it a Soviet puppet state, while Kurdish nationalist leaders Abdul Rahman Ghassemlou and Jalal Talabani emphasized Soviet friendship rather than control.
The republic controlled a small area in northwestern Iran, with Mahabad as its capital. Adjacent cities included Bukan, Oshnavieh, Piranshahr, and Naghadeh. The republic also claimed Urmia, Khoy, and Salmas, though those cities were held by the Azerbaijan People's Government.
The republic collapsed after the Soviet Union, under pressure from the United States and other Western powers, promised on the 26th of March 1946 to withdraw its forces from northwestern Iran. Without Soviet military and economic support, Kurdish tribal leaders who had backed Qazi Muhammad saw no reason to continue. The republic was economically bankrupt and its tribal coalition disintegrated before Iranian forces entered Mahabad in December 1946.
Mustafa Barzani, whose fighters from Iraqi Kurdistan had formed the backbone of the republic's forces, led several hundred soldiers on a five-week march and defeated Iranian army efforts to intercept them. They reached Soviet Azerbaijan safely. Officers from the Iraqi army who returned to Iraq were condemned to death and are honored today as martyrs for the Kurdish cause alongside Qazi Muhammad.