PL/SQL :: Queries Executed By A Session

I am trying to trace the SQL statements executed against a particular database user. I don't have AUDITING enabled and I am using Oracle 11g.I have the following query :

SELECT
S.MODULE,
SQL_TEXT ,
S.EXECUTIONS
FROM
[code].....

But if multiple users running the 'APP.EXE' are connected to the same db user, I am not able to understand which OS user executed which query. So I tried to join with V$SESSION view to get the user details.

SELECT
S.MODULE,SQL_TEXT ,SN.OSUSER, SN.MACHINE, S.EXECUTIONS
FROM
SYS.V_$SQL S,
SYS.ALL_USERS U,
V$SESSION SN
WHERE
S.PARSING_USER_ID=U.USER_ID
AND UPPER(U.USERNAME) IN ('USERNAME')
AND (UPPER(S.MODULE)='APP.EXE')
AND S.SQL_ID=SN.SQL_ID
ORDER BY S.LAST_LOAD_TIME

But this doesn't seems to be working(In my case it didn't return any rows) I have also tried the following

select S.SQL_TEXT,S.MODULE,S.EXECUTIONS,SN.OSUSER,SN.MACHINE,SN.SID, U.username,U.user_id from
SYS.V_$SQL S, v$open_cursor oc,SYS.ALL_USERS U,V$SESSION SN
where S.PARSING_USER_ID=U.USER_ID
AND UPPER(U.USERNAME) IN ('USERNAME')
AND (UPPER(S.MODULE)='APP.EXE')
and oc.SQL_ID=s.SQL_ID AND SN.SID=OC.SID AND SN.SADDR=OC.SADDR;

but I am not sure whether this is giving the right results. So, I have the following questions

1) How do I get the queries executed by each session?

2) The EXECUTIONS column of V_$SQL seems to the executions from all the sessions. How do I know the number of times a particular query is executed by a session?

3) How long a record about a query will be stored in V_$SQL? When do Oracle delete it from the view?