How To identify SQL command performance from V$ table

 Dear Sir:

      I have some question about Oracle dynamic performance view :

1. I can identify session performance (CPU usage) from v$session, V$sesstat, And I only can get disk reads, buffer gets indices of sql command, but I can not get any CPU performance data of sql command from V$sql, v$sqlarea, v$sqltext.. so, would you please tell me how can I get cpu usage performance data for sql command from v$ table, not from trace file.
2. did object will still in v$db_object_cache when it is age out library cache
3. how can I get object dependency relationship from V$session, v$sql, v$object_dependency because there is not relation key of v$object_dependency with v$session and v$sql

 Thanks a lot!

                               Roger Li