There are 2 problems with fcv change and the config settings schema. The first is that during fcv downgrade, we are checking the wrong feature flag to guard the config settings schema code. We need to use gConfigSettingsSchema rather than gGlobalIndexesShardingCatalog. The second is that during fcv downgrade, we are setting the schema to an empty schema and turning the validation level to off. When we upgrade, we add the correct schema, but this doesn't reset the validation level to the default, it stays as off. This means that downgrading and then re-upgrading will leave the validation level as off.