At the first time, I select English as the language. The touch screen worked but not the keyboard; it was irresponsive. Online updating resulted a failed code by the end of update process( after a long download).
At the second try, I selected to Vietnamse and update process successed. I'm not sure if the language was the problme, or it needs to be flash twice.
I'm glad that finally I turned a working phone to my Mom but that cannot not be done without the help from the following sources. Thank you, gals and guys!