Syd4r shared this tutorial with us: https://steamcommunity.com/sharedfiles/filedetails/?id=889624474 To download steam games in older versions. Thanks Syd4r

For ALTF4, speedruns recorded on older versions of the game using this technique will be counted as valid. This means that you can play by removing the patch of certain bugs for example.

Do not hesitate to give us your feedback on the subject.