Yes
If someone has not removed it, Then yes it is before the muffler.
Muffler should be after the cat.
Yes, legally and for the computer to function correctly you will need a catalytic converter.
If you remove a catalytic converter, you are breaking the law. It is a $2500 fine. It will not run right anyway, because of the oxygen sensor after the catalytic system. You are just going to get horrible fuel mileage if the cat is removed, and a check engine light that is annoying as hell.
Could be, A plugged fuel filter, A damaged/plugged catalytic converter, Fuel pump failure,
NO.
That is the sensor after the catalytic converter.
Under vehicle, passenger side, below seating area, front of catalytic converter, mounted in passenger side exhaust pipe.
With gas engine, yes. Not sure about diesels. Diesel, yes
4L80
That would be the 4L80E
does a 1992 Chevy 2500 2wd differential have a vent tube