Insurance companies are not going to pay more than the cost of boat even if something fails, like the mast, and the replacement cost is more than the value of the boat.
There are 2 basic types of hull insurance, Agreed Hull Value and Actual Hull Value. With Agreed Hull Value you and the insurance company (well mostly the insurance company) agree to a value that the boat is worth and if the boat is declared a Total Constructive Loss that is what you get. With Actual Hull Value, the insurance company will pay you the value of the boat just before the accident, which will likely be less than the price you paid for the boat. Under this policy the boat value is depreciated, under the Agreed Hull Value policy the boat is not depreciated. Needless to say the Agreed Hull Value policy is more expensive than the Actual Hull Value policy.
If you get a liability only policy and your boat is declared a total constructive loss, you get nothing.
Regardless of which type of policy you get, some things on your boat, such as rigging will be depreciated and you will get less than what you paid for the item or for its replacement cost.
Hull insurance will never make you whole again after a total constructive loss. It will pay for repairs and damage up to a reasonable percentage of the agreed value of the hull or the actual value.
Also, you will never get the insurance company to give you concrete definitive answer to any hypothetical question about loss or damage. Doing so might put them on the hook for something a poorly informed agent might say.
Expect to pay roughly 1-2% of the Agreed Hull Value for insurance. And like all insurance, your credit history and claims history will be a factor in the rate you pay.