I hope you’re joking...? An interface that forbids you from working unless you know an easter-egg/“insider” password is almost a fascist concept. I guess that’s another reason not to use Chrome...
For HSTS, it’s based on the spec. There’s not supposed to be a user-accessible override for HSTS errors, which is why Chrome hides it behind that easter egg. Firefox has no override of any kind.
It's just a shortcut to avoid clicking on two buttons.
No it isn't, for certain certificate errors this is the only way.