How to restore database object such as package body via flashback?

Note that below SQL gets output if it is still in UNDO tablespace.
SQL> 
SELECT text  FROM all_source
       AS OF TIMESTAMP TO_TIMESTAMP ('21-04-2017 14:30:00', 'DD-MM-YYYY HH24:MI:SS')
 WHERE name = 'PRG_BODY_ALPER' 
AND TYPE = 'PACKAGE BODY';

for DBA: dba_source table

Related: https://ozsoyler.blogspot.com/2016/12/how-to-rollback-committed-data-from.html

How to rollback committed data from flashback?

To Check
SQL>
SELECT *
  FROM HR.EMPLOYEES
       AS OF TIMESTAMP TO_TIMESTAMP ('2016-12-19 21:35:00', 'YYYY-MM-DD HH24:MI:SS')

To Save Data As Temp Table
SQL>
CREATE TABLE HR.EMPLOYEES_TEMP AS
SELECT *
  FROM HR.EMPLOYEES
       AS OF TIMESTAMP TO_TIMESTAMP ('2016-12-19 21:35:00', 'YYYY-MM-DD HH24:MI:SS')
-- WHERE EMPLOYEE_ID = 100