Grebenkin graduated from the Irkutsk Military Aerospace Engineering Institute with the qualification of "technician diploma" in the specialty "Technical operation of transport radio-electronics" on June 21, 2002.

In October 2019, as part of a conditional crew, together with Alexei Zubritsky and Evgeny Prokopyev, he went through a full cycle of "water survival" ("dry", "long" and "short" training) at the Universal Marine Terminal Base, "Imeretinsky", on the Black Sea in the Adler district of the city of Sochi.

[1] In July 2021, as part of a mock crew, together with Alexander Gorbunov and Alexei Zubritsky, he participated in a two-day training session to practice actions after landing a spacecraft in the desert.

[1] On January 20, 2022, at a meeting of the Roscosmos Interdepartmental Commission, he was approved as Flight Engineer 2 of the International Space Station Expedition 71.

They participated in training on actions after landing the spacecraft on the water surface, which took place on the basis of the 179th Center of the Ministry of Emergency Situations in Noginsk.

[1] On March 1, 2023, at a meeting of the Interdepartmental Commission of the State Corporation Roscosmos, he was appointed as a stand-in for cosmonaut Konstantin Borisov on the flight of the SpaceX Crew-7 mission and was included in the prime crew of the American spacecraft Crew Dragon (SpaceX Crew-8 mission), which launched to the ISS on 4 March 2024.