Database downgrade - MOS useful notes

Are you planning a database upgrade keeping a back-out (downgrade) plan in mid? Here are a few very important MOS docs explains all about:

• How To Downgrade From Database 11.2 To Previous Release (includes 11.2.0.3-11.2.0.1) [ID 883335.1]
• Database Server Upgrade/Downgrade Compatibility Matrix [ID 551141.1]
• Master Note For Oracle Database Downgrade [ID 1151427.1]
• Downgrading Database Without Executing catdwgrd.sql (11.1.0.x to 10.2.0.x/10.2.0.x to 10.2.0.x) [ID 783643.1]
• Complete Checklist For Downgrading The Database From 11.1 To Lower Releases [ID 443890.1]