If you want to see something interesting, assign your mesh’s parent Part a CFrame with an orthogonal reflection matrix for orientation, like Part.CFrame = CFrame(0,10,0,-1,0,0,0,-1,0,0,0,-1). 
This is not an intended feature, however, just a consequence of the ortho-normalization routine accepting already orthonormal matrices, as well as preserving a negative determinant of an orthogonal matrix through normalization. You don’t want to use this in a game though, the code could be updated at any time to keep things right-side out. It’s also not reliable; the part can be subject to re-normalization that flips it back right-side out if it has physics interactions. Rotating it with code or studio tools may also have unexpected results up to and including the part being collapsed out of existence. If you need an inside out part, you should make one with flipped normals and import it as a file mesh. Support for turning built-in meshes inside out is unlikely to ever be a common enough use case to be prioritized, and it’s easy enough to make inside out primitives with Blender.