It should be more like every tetrapod (four-limbed vertebrate that share ancestry with fish) has 4 limbs and 5-ish fingers configuration.

You are correct when you said that there are exceptions to this with some changes in fingers number and some animals with missing/vestigial limbs but the configuration it is generally true for most tetrapods. Some hooved mammals have one or two big fingers for their hooves because they evolved to loose their other digits over time. Marine mammals like whales are still considered therapods even though they do not really have back legs anymore but they still have the five finger configuration. Snakes are still considered tetrapod because their ancestors were reptiles that had all 4 limbs. It's kind of confusing and complicated, but generally the limb configuration is true for land-living vertebrates.

Insects and centipedes are not even vertebrates, so they do not have anatomy similar to tetrapods. It's kind of complicated but really cool to learn about once you get into it.