Whether well you remember nullable value types? We look "under a cowl"

Recently fashionable subject of nullable reference types steel. However old kind nullable value types anywhere did not get to also all as are actively used. Whether well you remember nuances of work with them? I suggest to refresh or check the knowledge, having studied this article. Code examples on C%23 and IL, appeals to the specification CLI and the CoreCLR code are applied. I suggest to begin with an interesting problem...