How to create a replica database

There are four ways to create a replica database.
1. Create from the active database, connect to the target instance and the secondary instance.

2. Create from backup, connect to target instance and secondary instance.

3. Created from backup, connected to secondary instance, not to target instance, but with recovery catalog connection.

4. Create from backup, connect to secondary instance, not to target instance and recovery catalog.
Creating a replica database using database replication technology always requires a secondary instance.