You wanna know what a 4D cube looks like? Look at pic related. Thats it.
The only difference is that the 4D cube can move between 3D planes. So if its on plane A and we are on plane B, we won't see it.
If its halfway between plane A and B, we could see a variation of things depending on how its split.
Thats if the cube has a 4d length of 0. If its longer than 0, there would always be a part of the cube thats not in our plane. But to us it would look no different.