If you meant Updating the Game. As long as you didn't Delete the whole Folder of this Game, you will not encounter any problems. But, I insist you to make a Copy of this Game's Folder in case you did something wrong so you will not lose all of your progress.
But, if you meant Reverting The Game to an Older Version. The Same as before. As long as you didn't Delete the whole Folder of this Game, I think your save files should still be intact.
If your save files were played on the latest update which is 0.90.13 and you wanted to go back and play it on version 0.90.10 your progress should be the same. But things like Content that got added on a Newer Version that you played before will not be there. as soon as you load your save, it should seem like it got deleted. (Or maybe shows up as a Missing Item just like when you uninstall a Mod.)
Just for an Example...
In The 0.90.13 Update, they added New Musician Hoodie Designs to the Game but in Version 0.87.11 they weren't there yet. So... If you revert the Game from Version 0.90.13 to 0.87.11, those Hoodies that you bought will no longer be there as soon as you load your save that you had recently played on the Newer Version.