Can we open a pluggable database if CDB is in mount state?

We cannot open a pluggable database if the CDB is in mount state.

Demo:

SQL> show con_name;

CON_NAME
------------------------------
CDB$ROOT
SQL> select name,open_mode from v$database;

NAME      OPEN_MODE
--------- --------------------
ORCL1210  MOUNTED

SQL> alter session set container=pdb1;

Session altered.

SQL> show con_name;

CON_NAME
------------------------------
PDB1
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-65054: Cannot open a pluggable database in the desired mode.


Now, I'm opening the container Database first and then running the same command

SQL> alter session set container=CDB$ROOT;

Session altered.

SQL> sho con_name

CON_NAME
------------------------------
CDB$ROOT
SQL> alter database open;

Database altered.

SQL> select name,open_mode from v$database;

NAME      OPEN_MODE
--------- --------------------
ORCL1210  READ WRITE

SQL>  alter session set container=pdb1;

Session altered.

SQL> sho con_name

CON_NAME
------------------------------
PDB1
SQL> alter database open;

Database altered.
SQL> select name,open_mode from v$pdbs;

NAME                           OPEN_MODE
------------------------------ ----------

PDB1                           READ WRITE