I am considering getting into train simulation, and I heard that buying an older copy of train sim and registering it with Steam will automatically update it. If I were to do this, will I get only the routes and trains of the original copy that I bought, the routes and trains of the original and the latest update, or the routes and trains of the original, latest update, and everything in between?
You’ll just get the routes that come with the the version you buy. The core program will update to the latest version.
One of the benefits of buying an older version of TS (ie TS2017) is that you can get some content that had been withdrawn due to licencing so the trains will still have branding on them rather than being unbranded. It's how I got copies of North Wales Coastal with Virgin branding and South Wales main line with Arriva Trains Wales branding.
