The answer is: it depends. If you knew that the policy was revised then you do have some responsibilities. My suggestion would be to show your policy to an insurance lawyer in your area as to how to proceed.
No, an insurance company can not apply an exclusion that it has not provided you with notice of the provision. I was involved in obtaining a bad faith judgment against a carrier that did not provide a copy of an insurance policy until after the loss occurred. The 7th circuit affirmed our position and a 1.2mm judgment.
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