Swelling at the point of the elbow

Because the swelling is outside the joint.

There is a thin cushion over the point of the elbow, between skin and bone. It fills with fluid when it is irritated. The joint underneath is usually untouched, so bending stays normal. That is a useful sign, not a puzzle.

Redness, heat and fever say yes.

A simple irritated bursa is a soft, fairly painless swelling. An infected one hurts to touch, is red and warm, and often follows a small break in the skin. If you are diabetic, assume it needs checking rather than watching.

Sometimes.

Where infection or gout is a question, taking a sample answers it. Draining a simple one gives relief but it refills if the leaning continues.

If the elbow goes back on the same table, yes.

The single thing that prevents recurrence is changing what the elbow rests on.