i am trying to use the wiring mode to stretch the wires -- How to control the minimum size of snapping ? Seems the BOX selected is lesser than the poly width + snapping doesnt seems as per grid size - how to control these ?

The wiring tool works by defining a square area and stretching it vertically or horizontally. It starts with whatever material it finds to start on, but in the case of a poly gate extension like you show above, that area might not be square, so it will start using the largest square that can fit in that gate extension area. Two solutions: 1) Place the cursor box in an area over the gate poly extension and type the command

fill s

to make sure the extension is longer than it is wide. After that, if you select using the wire tool, it will be the full width of the poly. 2) After starting a wire, use the mouse wheel to change the size of the wire.

Noted. I am able to do now with some practice