Reference:
https://docs.microsoft.com/en-us/azure/sql-database/sql-database-managed-instance SQL Managed Instance allows existing SQL Server customers to lift and shift their on-premises applications to the cloud with minimal application and database changes. At the same time, SQL Managed Instance preserves all PaaS capabilities (automatic patching and version updates, automated backups, high availability) that drastically reduce management overhead and TCO.
https://docs.microsoft.com/en-us/azure/azure-sql/managed-instance/transact-sql-tsql-differences-sql-server#clr
https://docs.microsoft.com/en-gb/azure/azure-sql/database/transact-sql-tsql-differences-sql-server#transact-sql-syntax-not-supported-in-azure-sql-database