> Question1. What is most common use case for having application root and application container PDBs ?
Sharing the data model of an application among multiple SaaS-customers,
providing separate development enviroments (with the same data model) for different developers,
Please see the docs for more information:
> Question2. Can a regular PDB can be plugged in to an application container in 12.2 ?
Existing applications (in a PDB) can be migrated into an application container;
> Question3. Can an application root can be unplugged from a CDB and plugged in to another CDB ?
for more information on application containers.
Thank You Markus