Try to set it up as new device, if necessary without using the latest backup:
1. There is no such thing as a "hard" (or "soft") reset in iPhone terminology. See the User Guide, Appendix B for info about iPhone troubleshooting steps
2. If you mean phone reset (press both home and on/off buttons until the Apple logo appears), no data is deleted from the phone.
3. If you actually mean "restore", all data is returned to the phone if you use a backup and sync. If you restore as new, without using a backup, some data is lost (messages, recent calls, contacts [if you aren't also syncing contacts], photos, etc.)
Thanks to all, friends!
In fact, I really hope to not reset. Just wondering, any solution for the "Auto-Shut Down" issue? seemed Nope?!
What I wish to reset is to resetting/revert to the factory setting of 3GS and check out whether the issue mentioned above disappear after that?
Any better idea?