[C++] Multiple Terrains Loading "Random" Height Maps from Directory

Edit: I do mean C#, not C++

I'm looking to create an arena based game with a few friends. I'm fairly inexperienced with coding in Unity, but I am looking to create a set of 9 tiles of 3 different sizes. Based on the type/size of tile I am looking to load a different type of terrain.
The goal of the map will be similar to this:

[table="width: 100, class: grid, align: center"]
[tr]
[td]2[/td]
[td]2[/td]
[td]N[/td]
[td]1[/td]
[td]1[/td]
[/tr]
[tr]
[td]2[/td]
[td]2[/td]
[td]N[/td]
[td]1[/td]
[td]1[/td]
[/tr]
[tr]
[td]W[/td]
[td]W[/td]
[td]C[/td]
[td]E[/td]
[td]E[/td]
[/tr]
[tr]
[td]3[/td]
[td]3[/td]
[td]S[/td]
[td]4[/td]
[td]4[/td]
[/tr]
[tr]
[td]3[/td]
[td]3[/td]
[td]S[/td]
[td]4[/td]
[td]4[/td]
[/tr]
[/table]

Where:

1. Numbers are playable areas
2. N,E,S, W are walls
3. C is the impassible center of them map.

I'm looking for a way to do the following with C# Scripts:

1. Select load a HeightMap at "Random" from a directory or folder
2. Rotate a terrain (I assume this is simple, I am just new to this)