1. The reason I am thinking to use SnapCreator is because of the automation requirement, so, can SnapCenter for Oracle-plug also allow me to schedule the process?
Yes, it is very similar to SnapCreator but more robust and more rich interms of features and GUI capabilities and work-flow automation. It will certainly allow you to schedule the process.
2. Is the SnapCenter for Oracle is the replacement of Snap Manager for Oracle?
Yes, these are basically plug-ins for SnapCenter server. All the Snap Manager products such as Exchange, SQL, Oracle etc will be phased out, some of them have already reached EOA. Instead, SnapCenter will be a one central management application server and rest all wil be plug-ins, basically replacing the SnapManager suite of products.
3. Not the lease, I am thinking now that I cannot use SnapCreator for DR, because the primary site would be gone in DR, whereas the clone DB could be set up on the DR site. So, I cannot use SC in DR scenerio. Am I right?
You can use snapcreator for DR, it is still a supported product, just that Snap Center is more rich as it is primarily replacing the SnapManager suite of products, and therefore it is much more sorted product. Regarding your query : Yes, you can clone DBs from the DR replicated copy of vault/mirror and then mount it as per the DB requirements.
List of SnapCenter components:
SnapCenter Plug-in for Oracle Database overview: