A: PGA itself is subdivided. The UGA (User Global Area) contains session state information, including stuff like package-level variables, cursor state, etc. Note that, with shared server, the UGA is in the SGA. It has to be, because shared server means that the session state needs to be accessible to all server processes, as any one of them could be assigned a particular session. However, with dedicated server (which likely what you're using), the UGA is allocated in the PGA.
C: The Location of a private SQL area depends on the type of connection established for a session. If a session is connected through a dedicated server, private SQL areas are located in the server process' PGA. However, if a session is connected through a shared server, part of the private SQL area is kept in the SGA.
Note:
* System global area (SGA)
The SGA is a group of shared memory structures, known as SGA components, that contain data and control information for one Oracle Database instance. The SGA is shared by all server and background processes. Examples of data stored in the SGA include cached data blocks and shared SQL areas.
* Program global area (PGA)
A PGA is a memory region that contains data and control information for a server process. It is nonshared memory created by Oracle Database when a server process is started. Access to the PGA is exclusive to the server process. There is one PGA for each server process. Background processes also allocate their own PGAs. The total memory used by all individual PGAs is known as the total instance PGA memory, and the collection of individual PGAs is referred to as the total instance PGA, or just instance PGA. You use database initialization parameters to set the size of the instance PGA, not individual PGAs.
References:

References:https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams240.htm#
REFRN10214

Explanation
References: https://docs.oracle.com/database/121/UPGRD/upgrade.htm#UPGRD52860

Explanation/Reference:
Explanation:
RMAN> ALTER TABLESPACE sysaux OFFLINE IMMEDIATE;
RMAN> RESTORE TABLESPACE sysaux;
RMAN> RECOVER TABLESPACE sysaux;
RMAN> ALTER TABLESPACE sysaux ONLINE;
* Example:
While evaluating the 12c beta3 I was not able to do the recover while testing “all pdb files lost”.
Cannot close the pdb as the system datafile was missing…
So only option to recover was:
Shutdown cdb (10)
startup mount; (1)
restore pluggable database
recover pluggable database
alter database open;
alter pluggable database name open;
Oracle support says: You should be able to close the pdb and restore/recover the system tablespace of PDB.
* Inconsistent backups are usually created by taking online database backups. You can also make an inconsistent backup by backing up data files while a database is closed, either:
/Immediately after the crash of an Oracle instance (or, in an Oracle RAC configuration, all instances)
/After shutting down the database using SHUTDOWN ABORT
Inconsistent backups are only useful if the database is in ARCHIVELOG mode and all archived redo logs created since the backup are available.
* Open the database with the RESETLOGS option after finishing recovery:
SQL> ALTER DATABASE OPEN RESETLOGS;