Hello, excuse me for haven't read well your post :( Most of the time when someone begin by "I am new to .." it means a question rather than an answer. 

Just to say your script is equivalent to that in Grasshopper component + sandbox for topology. 

In order to not use UV, you will have to use mesh TopologyVertices...

Thank you Laurent, I will look into TopologyVertices... I was writing a definition to get the surrounded vertices of a specific one...

TopologyVertices is a bit tricky, the numbering is not the same as the one used in the mesh. There is everything in RhinoCommon to cope with this. There are some ressources on this forum. 

http://www.grasshopper3d.com/forum/topics/mesh-topology-vertices

http://www.grasshopper3d.com/forum/topics/using-the-topology-functi...

Deconstruct mesh to vertices, deconstruct vertices (points) to X,Y,Z values. Sort Z values and then sort points at the same time. Use list item to find the first points on the list. Reverse list to find the last points on the list.