The issue was **Ground.exe**. It infected several programs and added “g” at the beginning for processes in Task Manager. Even Python wasn’t working.
* Defender Service was completely disabled and none of the Youtube guides worked.
* Installed AVG free and quarantined some files.
* Updated Windows with Update Assistant and now got Defender working.
AVG free now seem a bad move since the [Avast](https://in.pcmag.com/news-analysis/134853/the-cost-of-avasts-free-antivirus-companies-can-spy-on-your-clicks) privacy issues. AND THEY INSERTS THEIR SIGNATURE IN MY EMAIL (OPENED IN A BROWSER!) WITHOUT EVEN ASKING!!. But if I even put AVG in passive mode, Defender and whole system starts misbehaving. There are still infected files in the system, I presume. After reading some comments ,I see Kaspersky (Free or Pro?) AV is a good option. But would that solve virus and privacy issues?