How to Hard Reset Apple iPhone

Before you give your handset to repair shop or buy new handset, please try the following procedure to repair your device. First charge your battery more then 70%, backup your important data like phone-book, message, email, images and settings and in most cases take out SIM card and SD card. After doing hard reset not possible to recover your data, so online backup is always important. For all of your data, a backup should be done on a external device, hard drive, raid system media or SD card. 

If the device menus are frozen or unresponsive, you can soft reset using hardware keys. To perform a soft reset, follow these steps:

• Begin by holding the sleep/wake button at the top right of the device and the Home button at the bottom center of the face at the same time.
• Hold them both until you see the screen go black. In some cases, you may need to keep holding them even after the red power-off slider appears. If it appears, just keep holding it.
• Wait until the silver Apple logo appears.
• When this happens, you can let go - the iPhone is rebooting.

Update and Restore iPhone Software

You can use iTunes to update or restore iPhone software 

• Please installed the latest version of iTunes from www.apple.com/itunes.
• connect device to your Pc.
• In iTunes, select device in source panel and click the summary tab
• click Check the Update iTunes tell you if there's a latest version of the iPhone software available.
• click Update to install the latest version of the software. Or click Restore to restore iPhone 3GS to its original setting and erase all data on iPhone. 

Master reset from settings menu

A master reset restores the original factory settings and may delete your personal data on the internal storage, such as downloaded content, ringtones, images, apps, and contacts. It does not delete data stored on the SIM card or SD card.

To perform a master reset, follow these steps:

1. Back up all data on the internal memory.
2. From the Home screen, tap Settings.
3. Tap General.
4. Tap Reset.
5. Tap desired option:
• Reset All Settings
• Erase All Content and Settings
• Reset Network Settings
• Reset Keyboard Dictionary
• Reset Home Screen Layout
• Reset Location Warnings
6.  Tap the Erase All Content and Settings option second from the top, followed by the  Erase iPhone option in the resulting pop-up window to confirm the decision.

Apple iPhone DFU Mode

• Ensure the iPhone is off.
• Connect to Pc with sync cable/iTunes.
• Press and hold  the power button and also hold the home button.
• Release the power button while continuing to hold the home button.
• Now prompted that iTunes has detected the iPhone in recovery mode.