4
12 of then but if they are joined together in the form of a 6 sided hexagon then 6 endpoints are needed.
Only one.
12 lines
Segments.
No. Line segments end at the endpoints.
All line segments have exactly two endpoints.
5 lines
You need any number between 10 to 20 distinct end points.
No. They have 2.
6
There are 28 lines segments that both have their endpoints located at the vertices of a given cube.