what was the significance of the John Deere's first plow?

Answer 1

It was all steel. This was an improvement over the cast iron and wooden plows of the day, which were subject to breaking much more easily. It was durable and could be repaired much easier than other plows. It greatly improved the productivity of plowing.
I take that back. It wasn't "all steel", but all of the critical parts that would plow through the soil were steel. This plow made settling the Plains states a much easier, faster process.

Answer 2

John Deere

Answer 3

From Wikipedia,

in his father’s Rutland, Vt. tailor shop, Deere had polished and sharpened needles by running them through sand. This polishing helped the needles sew through tough leather.

He found that cast-iron plows were not working very well in the tough prairie soil found in Illinois, and remembering the polished needles, Deere came to the conclusion that a plow made out of highly polished steel and a correctly shaped moldboard (the self-scouring steel plow) would better be able to handle the soil conditions of the prairie, especially its sticky clay.

(Note: The old trick to get a diaper pin to penetrate, cloth diapers was to drag it through your hair to 'oil' the surface. Or was it the rough scalp?)