I just installed ZenUI launcher and somehow it fixed the problem in my Galaxy S3 Neo.
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Edit: My phone was able to start but whenever I tried to clear all the open apps by pressing the home button for 2 seconds, it showed this error message ''['com.android.systemui has stopped working, unfortunately']. ''
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So first I factory reset the phone, the error was gone. Then when google play store was restoring all my apps, the error message came back. After lots of hit and trial, I installed a Launcher and then just by installing (not even using it), the error was gone.