DB, Control, Redolog files location while Creating DB with DBCA

Question

I am creating DB with DBCA, and want to control locations of these files like
/u04/oradata/dbname/filename,
so can i put this in front of all in the section of file direcotry ?
2nd how i can check redolog file destination of existing DB with query/view?
Controlfiles
{ORACLE_BASE}\oradata\{DB_NAME}\
{ORACLE_BASE}\oradata\{DB_NAME}\
{ORACLE_BASE}\oradata\{DB_NAME}\
DB files
Filename File Directory
CWMLITE01.DBF {ORACLE_BASE}\oradata\{DB_NAME}\
SYSTEM01.DBF {ORACLE_BASE}\oradata\{DB_NAME}\
UNDOTBS01.DBF {ORACLE_BASE}\oradata\{DB_NAME}\
Redo Log Groups
REDO01.LOG {ORACLE_BASE}\oradata\{DB_NAME}\
REDO02.LOG {ORACLE_BASE}\oradata\{DB_NAME}\
REDO03.LOG {ORACLE_BASE}\oradata\{DB_NAME}\

Answer 1

to access newly created db through sqlplus , i have
to update, /etc/oratab?Not necessarily. If you want to use e.g. scripts that reference oratab or if you want dbca to "see" the db, then yes. It depends.
and then export oraclehome,
base, path, sid and access it or do have to adjustYes you need to set up your environment based on the instance and its Oracle Home. See the Install Guide (post install) and/or Administrator's Guide.
my listener will automatically register this new db?No, well, not really. The instance (pmon) will automatically register with the listener.