[3] In 2004 he finished runner-up in the U18 division of the World Youth Chess Championships.

[9] In February 2015, Tomashevsky took clear first place in the Tbilisi leg of the FIDE Grand Prix 2014–15 series scoring 8/11, 1½ points ahead of second-placed Dmitry Jakovenko, with no losses and wins over Baadur Jobava, Alexander Grischuk, Shakhriyar Mamedyarov, Maxime Vachier-Lagrave and Rustam Kasimdzhanov.

[11] In August 2015, he won the Russian Championship Superfinal in Chita, Zabaykalsky Krai with 7½/11.

[12] The following year, he played for bronze medal-winning team Russia in the 42nd Chess Olympiad in Baku.

In 2019 Tomashevsky won his second Russian Championship in Votkinsk – Izhevsk, Udmurtia with a score of 7/12.