Decapitation

In Mommie Dearest, why did they act like Julian could only be killed by the Phoenix Sword? Just because he was hundreds of years old, it didn't change the fact that he could still be killed by decapitation or a simple stake through the heart, which Stefan did several episodes later.

Im curious if Hope would be able to become alive as a tribrid if she had been decapitated. I mean, decapitation is a certain death.

So if you're a human and you die with the Gilbert ring on, you come back right? What happened if you got you heart ripped out, or if you get decapitated. Would you come back or are you just dead?

I know that the white oak stake is supposedly the only thing that can permanently kill an original but I couldn't help but imagine how weird it would be if their heads were chopped off if it would grow back.

I’m curious, they say that the WOS is the only thing that can kill an original, but what if they were decapitated or had their heart ripped out?