The link posted above was from before GDPR. If you can't see the betas in steam, read this link:
https://forum.paradoxplaza.com/forum/index.php?threads/how-to-roll-back-your-game-version.1121392/
https://forum.paradoxplaza.com/forum/index.php?threads/how-to-roll-back-your-game-version.1121392/