Webcam not working + OS (El Capitan) not reinstalling

I am still using a 2013 Macbook Pro Intel-i5, Initially, I had issues with my webcam driver (Facetime), all applications using webcam crashed (ie. Zoom, Facetime, Photobooth, Skype). But Facetime camera is working in iMovie. So, I tried to reset camera drivers from the Terminal using "sudo killall VDCAssistant" and "sudo killall AppleCameraAssistant" but still the same. When I checked system information, camera shows error in detecting devices but under USB, it is detecting Facetime HD camera. I tried to reset NVRam during reset and Repair OS using option+R. When I reinstalled the OS, it didn't accept at first because it said I have to install only in my country but was able to download the file for some reason. When it was in the process of reinstalling, it had an error and did not proceed, so it got cancelled. Now, when the system restarted, it can no longer proceed but kept on resetting due to kernel error: OS not set. Now, I ran out of options thus I resorted in sending this SOS message. Could this be a hardware or software problem?