I want to draw lines on grid graph, can I draw on it, How?
The simplest way to make a regular grid is to draw a texture shaped like a plus-sign. Use standard image tricks make sure the ends line up. Put that on a material with tiling x and y set pretty high (then, obviously, put it on a plane.) Can use Offset x/y to shift it to start on an edge.
It can be see-through if the original plus uses transparency.