3
One! That is what collinear means!
Just one.
Only one if they are non-collinear. An infinite number if they are collinear.
Three
3
One! That is what collinear means!
14
84 of them.
only 1 lines can contain 3 collinear points. Maybe you mean coplanar?
64 triangles
Just one.
Three
Points are collinear if they are on the same line.
The answer depends on how many points there are and how many triplets are non-collinear.
Two intersecting lines can always cover three non-collinear points.
7.