The door doesn't look crooked in the frame and the hinges don't look worn down. But if theres room at the top of the frame, you could lift the door by putting washers between the hinge parts. The decorative finials may be threaded into the hinge pin and need to be removed. But then the whole door should lift off of the lower part.

Is the door sticking on the frame or is it where the latch and striker meet? From your photo it looks like the latch is low on the striker. It also looks like the knob has slid down a bit from the paint around the escutcheon. If it is the latch try loosening the knob and lifting it up, or remove the striker and use a file to enlarge the hole.

As Bentresh said, all of our tech is the end of a long line. Without writing we have no history of the source for so many things. For me the most prevalent is textiles and cordage and basketry. In only a few instances do these items get preserved and yet we still use ropes and shoe laces and now we weave items out of carbon fiber.

The term refers to technological level and has no relation to intelligence. Stone age tech is more primitive than Bronze age which is less advanced than Iron. Primitive usually refers to societies who are at the Stone Age level of technology. The Maya were used stone edged weapons and the only metals they used were gold and silver. And yet they had advanced calendars and mathematics. Sadly most all of their many written codexes were burned by religious fanatics Catholic missionaries.

Those legs are bent plywood, in sanding off the varnish/urethane it would be easy to damage the thin surface coat. Your best option would be to paint it, rough the surface with synthetic steel wool, then prime with kilz or zinser then paint. If you want to keep the wood grain you could try over coating it with gel stain.