What does isGenuine check for?

If we revoke or delete a key, will isGenuine return false the next time it verifies with LimeLM servers?

Don't use IsGenuine(), instead use IsGenuineEx(...) (or, in some of the languages, IsGenuine() with multiple parameters).

Yes, it re-verifies with the activation servers (checks for revocation, deactivation, and product key deletion, and a number of other factors). It also gets the latest custom license fields: https://wyday.com/limelm/help/license-features/