What can animals with backbones do that animals without back bones cannot do?

They are not, actually. The reason for that because animals with external skeletons (exoskeletons) have more surface area for their muscles to bind onto, giving them more leverage and strength. Animals with internal skeletons have far less surface area for the muscles to bind onto, thus limiting their strength. The average healthy human can lift their own body weight. Something like, oh say your average rhino beetle can lift up to 850 times their own body weight! Huge difference, and it's all because of surface area. The downside to having an exo skeleton, however, is that you have a limit on how large you can grow. The bigger you get with an exoskeleton, the more exponentially you'll feel the force of gravity on you until you simply can't hold yourself up anymore.

There are animals that have no backbone, but also lack an exoskeleton. These animals tend to be squishy, but many of them can actually regenerate body parts. A perk, if you ask me.