So if I take off a mod and play normal Stardew Valley then after that I want to play modded Stardew Valley would everything that I did when I was playing Stardew Valley modded be deleted?
It wouldn't necessarily be deleted as such, but it's a good idea to keep modded and unmodded to different saves, espcially if you have mods that add new items or animals. Error items (caused by removing custom content mods) are no fun. Error animals have been known to crash the game.