Open the Settings app, select System > Notifications & actions > Turn system icons on or off, set the Power option to On:
Fix: Battery Icon Missing from Windows 10 Taskbar | Password Recovery

I...

It's quite odd.
Try to enable the built-in local administrator account, so you won't be locked out of your PC:
Administrator account - Enable or Disable in Windows 10 - Windows 10 Forums

Or...

Is your PC joined to a domain?
Try to reset your local group policy to default. Please refer to the OPTION THREE:
Local Group Policy - Reset to Default - Windows 7 Help Forums

Try the Microsoft start menu troubleshooter:
http://download.microsoft.com/download/F/2/2/F22D5FDB-59CD-4275-8C95-1BE17BF70B21/startmenu.diagcab

You should not assign full permissions to everyone.
Here's the default permissions for C:\Users on my computer:

103394

Before login, click the small eye symbol icon on the right corner of the password box, check if your typed password is correct.