try going into safemode with network and see if you have the same problems.
What computer model? try replacing the bios battery.
1. err_cert_authority_invalid on chrome
This connection is not private on edge, chrome
Http 500 on internet explorer
2.Automatically some web pages open up (amazon ,snapdeal,evo trackr, onclickads )
3.And sometimes Skype is installed without my permission.
4. System security is disabled after login even if I turn it on it goes to disabled mode, defender turns off
I have no problems with my date and time ,it is set as per internet and it is accurate.
Extensions: no recent extension,removed all of them
I even installed adwcleaner, avast pro,malwarebytes and removed all possible threats.
I tried all these in safe mode also
Please someone suggest a solution without reinstalling my windows 10