If I understand the question correctly, it is a net.
It's a cube.
tetrahedron
octahedron
Octohedron, or rhomboid.
a polyhedron
An eight-face polyhedron is called an octahedron.
What polyhedron has eight sides and all of the are equilateral triangle?
pentagon
An octahedron.
It's a cube.
tetrahedron
Yes
octahedron
You're an octagon.
A regular octahedron.
Octohedron, or rhomboid.
It is a definitional requirement. If any face is not flat, then it is not a polyhedron.