@FurryNutz: Is it dangerous if I do the recovery? I think there is no need to do that. The router is working fine. I just wanna upgrade the FW to use the Facebook integration function. Otherwise, it is not a must. Maybe I will do that step at the end. Thank you.
@Hard Harry: Thanks for the link. I will try it at home tonight. Just saw some bad results but I will let you know the final. I have no idea about the relationship between FW version / HW and the region language.