He joined state service as a junior clerk in 1823 in his home town of Ardatov, relocated to Saint Petersburg in 1826, retired in 1827 and lived by drawing advertising boards and later illustrations for Svinyin publishing house.

Svinyin financed his study tour of Russia; in 1829, Gornostaev applied into the class of Alessandro Brullo at the Imperial Academy of Arts and served as his apprentice on construction of Mikhailovsky Theater (1831).

He returned in 1838, the year when Nicholas I announced to the Academy that "To retain the spirit of ancient Byzantine architecture in church designs, architects should follow the drafts of Konstantin Thon" ("Государь император повелеть соизволил, дабы при составлении проектов церквей сохранить вкус древневизантийского зодчества, руководствоваться чертежами К.

As critic Vladimir Stasov put it, "He was already 45, a professor, well established among unanimous copying and mimicking of classical European, Greek and Roman styles, when suddenly, influenced by educated or independently-speaking clergy, took a sharp turn... Gornostaev despised official, fake Russian, Thon's style" ("Он уже был профессор, человек 45 лет, давно подвизавшийся на поприще всеобщего копирования и переобезьяничанья классических европейских стилей, греческих и римских, когда вдруг, под влиянием знакомства с образованным или самостоятельным нашим духовенством, круто поворотил на другую дорогу... Горностаеву был тошен официальный, лже-русский, тоновский стиль").

Shortly before his death, he designed and built improvements to Trinity-Sergius Convent in Strelna (near Saint Petersburg) – entrance gates, a chapel and two residential buildings.