Can i add my registered vehicle to someone elses policy?

No. The named insured must be the vehicle owner. You cannot add your vehicle to another person's policy. If you do, the insurance company cannot pay any claims under the other person's policy because you have no contractual agreement with the insurance company and the other person cannot receive money as they are not the vehicle owner. The only exception to this is in the case of immediate family who reside together. All drivers must also be listed on the policy to have coverage.