When you buy a legitimate key from Steam, Humble Bundle, or a licensed retailer, that key activates the base game. Once activated, Steam automatically downloads the latest live version (currently 1.49 or higher).
Just remember: It is a marketing trap. Buy the standard game and use Steam’s free "Betas" tab to roll back the clock. Euro Truck Simulator 2 Product Key Version 1.40.4.8
Now, get back behind the wheel. Your delivery to Milan is waiting. When you buy a legitimate key from Steam,