almost time for breakfast, so let me give you quick answers to 5 and 4.
Generally there are 2 set screws that are in the rear of the base that grip the shaft of lolllip hinges
a little hard to get to and you will want a falshlingt and a longish secrewdriver, but I've often got them with a Swiss army knife in a pinch.
4. What ever you guy makesure it has bobbins , ( shuttle if neeeded for virbating shuttle machines) and bobbin cases. and a bobbin slide unles you want to parts chase.
Many owners have no idea what should be under the needle ares. Ahh I hear butter slicing.
.