Default Help needed in installing android OS.

Hey all. Hope you all are doing well. I need your help. A foolish mobile mechanic flashed out my Galaxy s4 gt-i9500 china , now my cell is just turning on and off automatically while connecting to my PC. I can't enter in recovery mode or odin mode etc while pressing selective key combination. volume down + home+power. Please help me, how can i connect my phone with my pc and install android OS.

thanx in advance....