After I upgraded from os2008 to Diablo, I found that all the application that I installed disappeared. I guess the upgrade doesn't include carrying the previously installed application over.

But what I really don't understand is that, now under the "installable apolication" of Application Manager, there are a lot of fewer applications than were there under OS2008. What can I do to correct this?

Well, first off, you'll need to enable the extras repository; it should be there in the application catalog, but not enabled.
There are also a few apps that were in Chinook extras that haven't made it to Diablo extras yet; these should mainly work, and you can even add that repo manually, but it's better to keep it clean unless you need something from there.

http://wiki.maemo.org/Extras

That is what the backup is for (in addition to backup up). When you restore it goes out and pulls down the latest (and hopefully works in diablo) so you get back to where you were. It worked that way for me.

Thanks, I've not though that backup could restore my old application.

My question is .. Under Os 2008, I've attempted to modify the system in order to have Chinese font for the browser. If I run the backup, will it restore those changes that I made to system that I no longer need, (Diablo's browser already came with Chinese support)?

Diablo's browser already came with Chinese support? Answer, is YES.

I think I wasn't clear. My question wasn't about whether the browser in Diablo supports Chinese.

My question was what exactly the restore from the backup does. It would be nice, if it only restores the applications I installed, but not all the unsuccessful changes I made to the system to get Chinese font in os2008.