[General Questions and Answers] visheshtungare0879:
complete basic information u should knw before doing anything to u device!!!!!!!!!

Download mode

Download mode is used to flash new ROM or custom ROM firmware. (See Flashing)

To enter download mode, turn off the phone and then hold down Volume Down + Home + Power.

If done properly within at least 8 seconds will reboot the phone.

If you can't enter the download mode your phone might be Soft-Bricked.

recovery mode

Recovery mode is used to install system updates in form of update.zip files (such as the one for rooting your phone), performing a factory reset and wiping the cache.

"Android out of the box" icon indicating successfully booted recovery mode

To enter recovery mode, turn off the phone, connect the USB cable, and then hold down Volume Up + Power.

If done properly, the phone will show the SAMSUNG and Galaxy S Plus screens and then end up at the "Android out of the box screen". Now press Menu to enter recovery mode.

The options for actually performing recovery when something is wrong with your phone are very limited with the stock recovery that comes preinstalled on your phone. However, you have the option to replace it with a much better, fully-featured recovery called "ClockworkMod Recovery" (CWM).

Getting into recovery mode can be a bit fiddly and you might need several tries. Connecting the USB cable makes it a lot easier. CWM recovery does not have this problem and boots reliably. If you are still having problems getting into recovery mode, download Easy Reboot Recovery.zip, unpack and run RebootRecovery.bat while your phone is connected with the USB cable. The phone will reboot into recovery mode.

Navigation in recovery mode is done using the Volume Up and Volume Down buttons to scroll up and down in lists and the Home button for choosing an item. Sometimes a simple push of the Home button is interpreted as two pushes so be careful.

Recovery mode is a separate partition on your device (#13) that holds its own minimal Android system with a kernel and a small set of tools.

rooting

Rooting allows apps to act as administrator of your phone (called "root") and perform modifications on anything. This allows you to use backup apps that can backup all apps including their data on your phone, firewall apps that control internet access for other apps, adblockers which block ads on webpages and inside apps and much much more. You control which apps you want to grant the root privilege to with an app called "Superuser". Please inform yourself on responsible use of root privileges and do not grant unknown or suspicious apps root rights.

All Custom ROMs, CyanogenMod-based ROMs etc. come pre-rooted. The rooting procedure is only necessary if you are using a stock Samsung ROM.

how to root

Easy rooting and unrooting guide by KeksKlip: http://xdaforums.com/showthread.php?t=1253707

Put Root-i9001-Signed.zip into internal sdcard

Reboot into recovery mode by turning on the phone while pressing Volume Up and Power Button

As soon as the "Android out of the Box" appears, press the Menu button

Use Volume buttons to choose "apply update from sdcard" in the recovery menu.

Press Home button to submit.

Use Volume buttons to choose Root-i9001-Signed.zip on sdcard

Press Home button to start update.

Choose "reboot system now" and press Home button to reboot your phone.

Unrooting is exactly the same, except with the file UnRoot-i9001-Signed.zip

hit thanks if i helped !!!