“Most of the European territory that became the USSR was handed to them at Versailles.”
Russia got nothing from Versailles - they were excluded from it; the territory the Germans took, as well as additional territory, was used to create the new (sometimes “renewed”) states of Finland, Latvia, Lithuania, Estonia, and Poland.
And Belorus, Ukraine, plus parts of Czechoslovakia and Romania. And from the territories of the Ottomans: Trans-Caucases Republic [Georgia, Armenia, Azerbaijan].