Fraud is unlikely since you'll be dead when a claim is filed. IINM After two years I believe they have to pay claims unless they can prove you intentionally lied.
Right. Material misrepresentation is the only way they get out of it after 2 years. If someone says they never smoked but then the autopsy turns up black lungs, all they can do is retroactively change the premium. If someone says they never had cancer and die of cancer, then it's cancelled.
I would recommend being completely honest. The insurance companies can well afford to fight for years in court if they feel like it, even if they know they'll eventually lose. The beneficiaries will not be grateful if they have to fight against a contested policy