We do use magnet generators. Every electrical generator is built on magnetic fields, and this is the way we obtain most of our electric power. However, we need to use energy to move these magnets. They’re just not moving themselves.
It is possible to provide a number of pages of mathematical proofs to show that these gadgets don’t work. However, the evidence is more real-world: make one for yourself, and observe the way they fail. There’s an entire subcategory of Youtube of people using fake devices to promote their videos which is quite impressive. I’m not sure what drives people to spend so much effort making these fakes however they’re easy enough to duplicate at home. However, once you’ve done it you fail, they’re a mystery. work.
The reason why the magnetic structure that you have mentioned is due to a fundamental law of field, which states that you aren’t able to return to the same location without at least the same amount of energy as you put in. For instance, if there are two north poles that face one another, they’ll be pushed away. However, placing a third, similar north pole-facing magnet in the same spot will require applying force, regardless of the route you choose to take. This force must be as strong than the force that pushes the first one away, which means it will not spin until you force it to spin. It’s impossible to “sneak out” the magnet because their fields are radiated everywhere and there is no way to overcome this. That is, unless you put into even more energy.