Both unilateral and bilateral contracts are enforceable in court. For example, a unilateral contract is enforceable when someone chooses to begin fulfilling the act demanded by the promisor. A bilateral contract is enforceable from the get-go; both parties are bound the promise.
Yes, scratching is a form of self harm. Try to tackle this problem while you can because it has the potential to get worse. I started out scratching and now I burn myself with a lighter and cut myself. It's a self-destructive way to deal with overwhelming mental/emotional pain.
A cat doesn't scratch to give you grief. A cat scratches because it's a form of exercise for the cat's muscles from the claws right through to the legs, shoulders, and down the back. In addition, scratching also sharpens cats' claws and cleans the exterior sheath.