What is SMOG?

Literally,  smoke + fog= smog.
Smoke is the collection of unburnt fuel particles suspended in the air.
Fog is the suspended water particles in the air.
The combination of these suspended particles gives the smog.

Does specific resistance/resistvity change on stretching a wire?

Specific resistance or resistivity is the resistance of a wire of unit length and unit area of cross-section.

It depends on two factors.
1. Nature of the substance.
2.  Temperature of the substance

It is not effected by
1. Length of the wire.
2. Area of cross-section of the wire.

So., when you stretch a  wire its RESISTIVITY remains constant.