Yes. If points are on the same side of a line, they are in a half-plane.
A plane is named by three points in the plane that is not on the same line.
Points that are collinear will be located on the same line. A line is a subset of a plane. Therefore, Yes, points that are collinear will be located on the same plane.
Not necessarily. Coplanar means that points lie on the same plane whereas collinear means that points lie on the same line. Points on a plane do not necessarily lie along the same line.
points that lines in the same plane are coplanor
There are no planes containing any number of given points. Two points not the same define a line. Three points not in a line define a plane. For four or more points to lie in the same plane, three can be arbitrary but not on the same line, but the fourth (and so on) points must lie in that same plane.
If it is a straight line it must be in the same plane. Otherwise not necessarily.
Any three points that are non-collinear (not on the same line) will determine a plane.