You do not need a new key to play 1.31 or 1.35. If you own the game on Steam, you can "time travel" to these versions for free using the Beta Tab in the game properties.
Right-click the game in your library > Properties > Betas > Select "temporary_1_31" or "temporary_1_35". Euro Truck Simulator 2 Version 1.35 1.31 Product Key
Sites promising free product keys for specific versions are often scams or contain malware. To play safely, always use a retail key from a verified seller. Why Play Older Versions? You do not need a new key to play 1
Adding a personalized touch to your GPS instructions. Understanding the "Product Key" Requirement Sites promising free product keys for specific versions
There is no specific "version key." A single legitimate product key (usually purchased via Steam or the official ETS2 website) unlocks the entire game.
Massive updates to Germany and the addition of new roads in France and Scandinavia.
In this article, we’ll break down what made these versions special and the legitimate way to handle product keys and version downgrades. The Evolution: From 1.31 to 1.35 Version 1.31: The Power of Choice