Is it ok to put Lime down in your backyard to keep away spiders, flees, ticks. Will it hurt your?

Yeah its fine. They will probably lick it once just to see what it tastes like, but they will probably hate it because of its super strong taste. Imagine what it tastes like ×100 sourness. That's what it is for dogs. It isn't bad for them and they wont eat it anyways.