Does DTS support building a MySQL instance locally as a slave library for RDS instance?

Yes. In the hybrid cloud scenario, users can create incremental migration tasks or submit Ticket to build synchronization tasks.

How to realize database disaster recovery?

You can realize database disaster recovery through data synchronization. That is to purchase an instance of the same origin and specification for disaster recovery,and then realize real-time data synchronization between two instances through DTS.

Can data synchronization modify the synchronization source instance?

The configuration of the source instance is allowed to be modified before the data synchronization task starts, and the source instance cannot be modified after the task runs.