To active your iphone 3GS or 4S iPhone’s spelling suggestions keyboard, works with the following steps:
1. Download iBackupBot at frist.
2. After download the backup, don’t run it yet.
3. Plug in your iPhone 3GS or iPhone 4S with iOS5 and click on the device
iPhone 3GS and 4S Spelling Suggestions Keyboard
4. Now Choose to “Backup to this computer” and click to “Sync”.
5. Install and run the iBackupBot and click on the latest backup for iPhone 3GS or iPhone 4S
6. Click “Path” to locate the following address “Library/Preferences/com.apple.keyboard.plist”
7. A new dialog box open and click “Cancel” 
8. Under the line “”, insert another following line, “
“
9. Now save the files and exits.
10. GO to iBackupBot menu and click “File” from there. Choose “Restore” fro the menu and for the iPhone to restart after the restore is complete. It takes some while, be patient.
Warning: The spelling predictions of this keyboard aren’t so good as expected but can able to impressed your friends. And don’t forget to type “confirm” when you select from the suggestions.