With changing "identity:false" to "identity:false" issue, a better way to solve it is to "re-create" the tables. Because _MigrationHistory Table records all the modifications we made from migration, so we cannot change previous setting (especially our initialModel) later by using migrations. So we need to clear _MigrationHistory, and this is how code-first entity framework works.

Furthermore, we can also use Package Manager Console to go back to previous Migration version. There are two ways to do that.
First, using a new database.
    1. Checkout the older version.
    2. Change the db name in the connection string.
    3. Update-database.
Second, using an existing database.
    Using pm command with a switch: update-database -TargetMigration: Target-migration-name