Final answer:
Ivan IV, also known as Ivan the Terrible, was the first to declare himself Tsar of all Russias and annexed various khanates, but he did not create St. Petersburg, the serfs, socialism, or the Eastern Orthodox Church.
Step-by-step explanation:
Ivan IV and His Legacy
Ivan IV, known as Ivan the Terrible, is credited with the annexation of various khanates such as Kazan, Astrakhan, and Siberia, and is famous for his harsh rule and establishment of a centralized Russian state. However, to answer the question more directly, he is not credited with any of the mentioned achievements such as creating St. Petersburg, the class known as serfs, socialism, or the Eastern Orthodox Church. The establishment of St. Petersburg was achieved under the rule of Czar Peter the Great in the 18th century, the class of serfs existed in Russia prior to Ivan IV but was later emancipated by Tsar Alexander II in 1861. Socialism was a concept that was developed much later than Ivan IV's time, and the Eastern Orthodox Church had been a significant part of Russian life for centuries before Ivan IV became Tsar.