The crashes most likely depend on the deleted old clothes (actually, in every version there's a warning about getting rid of clothes and saves).
I just did a quick try.
Dwloaded the 4-stable version, and started a new game.
When I went to save, my old saves (from the previous 4 version) were there too.
Saved anyways on a empty slot, and kept playing, and instant crash when tried to enter a building.
So, the game evidently looks for saves even if there are two versions of the game ond ifferent folders. In my case, I have a "Lifeplay" folder, and iside there are two folders, each is the older and latest version. Might worth trying to have every version on a completely different folder, to avoid the game looking for saves.
Aside of that, the saves are just for characters, so maybe there's a "game" save somewhere else? Lots of games have a "hidden" folder inside the windows system for example, and a separate save folder for character only, inside the game itself system. This could be the case?
Following that, it is possible to do a backup of the character saves (on a different location, let's say teh desktop). Start a full new game deleting any old saves to start clean, and then simply copy-paste the backup saves data on fresh new characters (basically, let's say you had a sister, and have a new one, just copy the data of the old one. Character data is only the stats and morphs, so there shouldn't be problems with old/new clothes or items)