Short answers, pulled from the story.
Simeon I of Bulgaria was the first monarch to adopt the title of tsar. He was crowned in a makeshift imperial ceremony performed by the Patriarch of Constantinople in 913, and the Byzantine government formally recognized his imperial title in 924 and again at the peace settlement of 927.
Tsar is derived from the Latin title caesar, used for Roman emperors. It entered Slavic languages through the Gothic term kaisar and was used as an equivalent of the Greek basileus, which referred to Byzantine emperors and the kings of the Bible.
Ivan IV, known as Ivan the Terrible, was formally crowned tsar of all Russia in 1547. He was the first Russian ruler to receive this official coronation, though earlier grand princes such as Ivan III had used the title informally in foreign diplomatic correspondence from about 1476 onward.
Simeon II was the last tsar of Bulgaria, holding the title until the abolition of the Bulgarian monarchy in 1946. As of 2026, he is the only living person to have held the title of tsar.
The metaphorical use of czar for positions of high authority dates to 1866 in English, when it was applied to U.S. President Andrew Johnson. One formalized early use was for Judge Kenesaw Mountain Landis, named commissioner of baseball with broad powers after the Black Sox scandal of 1919. The term later became common for senior government roles such as the drug czar and cybersecurity czar.
Tsar entered Slavic usage as an equivalent of basileus, the Greek title for Byzantine emperors and the kings of the Bible. In Bulgarian and Serbian usage, adopting the title was a direct challenge to Byzantine authority. In Russian usage during most of the medieval period, the title carried primarily religious or moral value rather than a claim to equal imperial status with Constantinople.