In diffraction, when wavelength is less than slit width, then does the scattered light gets absorbed & emitted from the wall or just rebound?
Some of the photons will hit the material beside the slit and will be absorbed by electrons of the wall. The re-emission will happens with different wavelengths, mostly in the infrared.
Photons will go through the slit uninfluenced beginning with some slits width. A simpler description of particle deflection is the case of a single edge. Here the slits width is infinite. But an intensity distribution behind the edge still appears.
For photons the first peak is equally distributed to the left and right of the geometrical shadow line. For electrons the first peak is right from a left edge, so electrons get only deflected from the edge meanwhile photons get deflected also behind the slit. This phenomena will be helpful to answer your questions.
H. Boersch FRESNELSCHE Elektronenbeugung 1940 (description of these experiments)
As you suggested, the interest should be focused to what you call rebounding.
... or the photon rebounces without interaction with wall?
A photon has an altering electric field component. It should be permissible to assume that by this field some photons interacts with the electric field of the surface electrons of the slits material. This are the photons which are not hitting the wall and not going uninfluenced through.
Since both the negative and the positive value of the photons electric field are involved, some photons arrive the observation screen behind the geometrical shadow and some arrive away from this line. Not so electrons, the all get deflected (in some range of distance to the edge) due to their always negative electrical potential away from this line.
This different behavior of photons and electrons at edges should be a very important argument for the interaction of the edges field and the particles field.