[PC/STEAM] Is there any way to access previous builds of the game?

To whom it may concern,

Regardless of my hesitance to post (after seeing the... low response rate of actual developers or Obsidian staff members), I guess I'm writing this down anyway. I speedrun games - it's a hobby and passion of mine, and has been for several years. I have run many games, worked with developers of several of these games, and even had the opportunity to attend Summer Games Done Quick 2016, a charity event that raised quite a lot of money for Doctors Without Borders, a non-profit organization that focuses on bettering the amount of medical care in places where it would otherwise be impossible to receive medical attention. Regardless of all the rambling, I love it. 

I recently came across a route for South Park: The Stick of Truth in which it is theoretically possible to finish the game in under one hour and 15 minutes (in a perfect run). You can see a video of said route here (standard Youtube link). In the run, however, we utilize several... unintended effects in order to beat the game as fast as we possibly can. Sadly, however, Obsidian, as of any Build Version higher than 1353, removed many of these (let's call them what they are) exploits we make use of in the run. Even worse, possibly, is the fact that anyone who wishes to learn/run SP: TSoT simply cannot without having access to the game's previous versions (anything pre-1353). 

This is my question: are there any methods, legal of course, in which players, who wish to do so, may "downpatch" their game to previous build versions to allow speedruning at the highest level?

I can understand if this is not a high-priority question, or even irrelevant. Developing games is a hard thing to do, and appealing to everyone is damn-near impossible. I just wanted to ask before I give up on running the game due to this unfortunate but uncontrollable situation.