In order to hard reset a Samsung I9001 Galaxy S Plus, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Samsung I9001 Galaxy S Plus device will be brought back to the default configuration of a brand new device.
1. Switch off the phone by press-holding the Power button.
2. Press and hold the Volume Up + Power + Home buttons until the Samsung logo pops onscreen.
3. Enter Recovery Mode by pressing the "sensitive button".
4. Using Volume buttons to navigate to it and Home button to select it, choose Wipe data/Factory reset option.
5. Next, select Yes and Reboot system now.
6. Yay, the hard reset process is complete.