Forms 10gR2 new internal pl/sql encoding

Sometimes, I see some posts on forums about Oracle Forms "downgrading" possibilities.
Questions like:

• I have lost the source modules (*.??B), can I retrofit from the executable modules (*.??X) ?
  The answer is:  NO
  
• I have just migrated from Forms 9i to Forms 10gR2. For any reason, I have to open/compile my new 10gR2 modules with the previous 9i tools, then I get the message : PL/SQL encoding has an unrecognized format !
  The answer is: always, always and always do backup copies of everything before doing anything !

In a general way, old versions cannot open/read newer modules.
As a matter of fact, the Forms 10gR2 (10.1.2) uses a new internal pl/sql encoding format that is not recognized by the previous versions.
So, think to backup !