Why there are five Platonic Solids?
Can we have a "semi"-Platonic Solids?
There are only five Platonic Solids and it's been proven.
I refer you to the wiki which gives two proofs: one geometric and one topological proof.
https://en.wikipedia.org/wiki/Platon...eometric_proof
I have no idea what you mean by "semi"-Platonic solids. A Platonic solid is a regular, convex polyhedron. Which of these conditions (regular or convex) did you want to drop?
Do you mean Archimedian solids? (semi-regular convex polyhedra)
https://en.wikipedia.org/wiki/Archimedean_solid