Who is liable for losses if insurance claims are denied?

If my car, previously used exclusively for private purposes, is now leased via ZoomCar and meets with an accident, what happens if the insurance claim is denied by the insurer citing the absence of a T-permit, thereby violating the terms for commercial use? Who would be liable for my losses in such a scenario? Additionally, if I hand over the vehicle keys to a guest, who then vanishes without a trace, and the insurer rejects a theft claim due to the handover, who would be responsible for making good my losses? Lastly, if my vehicle meets with an accident and the claim is either denied or partially settled by the insurer, and the guest denies responsibility and absconds, who would be liable for covering my losses?