Before you skip on buying car insurance, you should consider the penalties. Regulations differ from one state to another, but all of them involve a fine of up to a few hundred dollars and, upon the second or third offense, suspension of your driver’s license and even the impoundment of the car for which you failed to show proof of insurance.
It depends on where you are going to store the car you aren’t going to drive. Most states don’t accept unregistered cars parked on the road, but it might be alright to store it in the backyard or in a garage. You should, however, consider a limited-use policy if you plan on driving it every once in a while.
Yes, provided you are a non-excluded driver on that car (someone who has been specifically excluded on the owner’s policy and not permitted to drive the car). Should an accident happen, the car owner’s liability insurance will take primary coverage status and yours – if any – will act as secondary coverage.