How to open Oracle listener for three database instances?
Ok, I would like to answer my question. As i have understood what wrong I have done. 

I created 3 database instances. So I should start 3 database instance one by one. 

So how do we start 3 database instances?

every database instance has its own SID, so before you start the database, you need to put the 
correct SID for that. 

this is how i did it

ora112@localhost ~]$ ORACLE_SID=JIP02T
[ora112@localhost ~]$ ls
db.rsp  Desktop  summary
[ora112@localhost ~]$ sqlplus '/as sysdba'

SQL*Plus: Release 11.2.0.3.0 Production on Thu Dec 27 01:23:35 2012

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to an idle instance.

SQL&gt; startup
ORACLE instance started.

Total System Global Area 5511979008 bytes
Fixed Size                  2238056 bytes
Variable Size            1107298712 bytes
Database Buffers         4378853376 bytes
Redo Buffers               23588864 bytes
Database mounted.
Database opened.
SQL&gt; exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64                                                                             bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options


Then i need to set the SID for other database instance.

ora112@localhost ~]$ ORACLE_SID=JIP04K
[ora112@localhost ~]$ ls
db.rsp  Desktop  summary
[ora112@localhost ~]$ sqlplus '/as sysdba'

SQL*Plus: Release 11.2.0.3.0 Production on Thu Dec 27 01:23:35 2012

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to an idle instance.

SQL&gt; startup
ORACLE instance started.

Total System Global Area 5511979008 bytes
Fixed Size                  2238056 bytes
Variable Size            1107298712 bytes
Database Buffers         4378853376 bytes
Redo Buffers               23588864 bytes
Database mounted.
Database opened.
SQL&gt; exit


Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64                                                                             bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options


There after i just started the oracle listener, oracle listener is opened on port 1521.

So, using sql developer, i created 2 database connections to the two database instances using same port number 1521.