Do different eggs take longer to hatch?

Question

Do eggs take longer to hatch depending on what species of Pokémon is inside?

Answer 1

Yes, they do. These are known as Egg Cycles. Some Pokemon are rather quick and some take a very long time.

For example, Magikarp will hatch after just 6 Egg Cycles, which is a low 1530 steps, and despite not being able to be in an Egg legitimately, legendaries have Egg Cycles coded, and some of them require 121 cycles, or 30855 steps.

*= at minimum. Certain happenings can reset the current Egg Cycle, making it take longer for Eggs to hatch.

Source: Bulbapedia / experience.

Answer 2

yes
different species take different time
harder ones include rare and strong Pokemon
easier ones take shorter time like magikarp

Answer 3

based on my observations, yes.
for example:
shelmet:16 egg cycles minimum 4,080 steps
machop: 21 " " " 5,355 "