These are the instructions to root Samsung Galaxy S2 Plus GT-I9105 (running on android 4.1.2, 4.2.2) using Kingo Root Application on Windows Computer.
Requirements: Your Samsung Galaxy Grand Quattro GT-I8552 should have at-least 20-30 percent battery to perform the rooting process.
Step 1: Enable USB Debugging on your Samsung GT-I9105 Smartphone. To enable USB debugging, Open Settings > Developers Option > USB Debugging > Tick to Enable.
(Developers Option is hidden for Android 4.2.2 or above, to unhide Go to Settings > About Phone > Built Number (Tap on it for 5-8 times).
Step 2: Download and install Kingo Root Application on your Windows Computer.
Step 3: Once Kingo Root Application is installed on your Computer, Open It.
Step 4: Once Kingo Root Application is launched, connect your Samsung GT-I9105 smartphone to the computer.
Step 5: Once Your Samsung Galaxy S2 Plus GT-I9105 Smartphone is connected successfully to the computer, Kingo Root will automatically detect your Smartphone and install the necessary drivers.
Step 6: Now, Click on the “Root” button to begin the rooting process.
Step 7: Now, Kingo Root will root your Samsung Galaxy S2 Plus GT-I9105 and install the SuperSU Application.
Step 8: Once rooting procedure is completed you will be able to see Finish Button. Click on finish button to reboot your device automatically.
Step 9: Now your Samsung Galaxy S2 Plus GT-I9105 is Rooted. To check whether your phone is rooted correctly, open Applications Menu, there you will be able to see a new app installed, called SuperSU. If this app exist then it means you have successfully rooted your device.
Optional: You can also verify the root status of your device by using the Root Checker Application.
[*] No data loss process: Your Android Phone Data like contacts, pictures, videos, music and etc will be not affected with this method.
[*] Warranty Void: Your Android Device Warranty may be Void after following the above tutorial.
[*] Samsung Stock Firmware: If you are looking for the original firmware for your device then head over to Download Samsung Stock Firmware for all devices page.
[*] Samsung USB Driver: If you are looking for the original USB Driver for your device then head over to Download Samsung USB Driver for all devices page.
[*] Credits: Kingo Root Application is created by Kingo (Developer). So full credits for the above tutorial goes to the developer.