if i already download GRD images to find displacement , through a Rus tutorial the instructor used SLC images Iw1,2,3 then she splits the interested burns , the question is can I do the same steps for GRD and subset my interest zone , or for displacement we must downloads SLC images and flow the same steps

Yes, you need SLC data for inteferometric analyses, because it contains intensity and phase information. The latter is required for InSAR, but not contained in GRD data.

do you have explanation for every time I try to download images from Copernicus Open Access Hub , after I choose IW , SLC they don’t found my request , they only insert images for no specific parameters

yes, because you selected HH polarization which is barely available. 99% of Sentinel-1 data is VV polarized.

thanks a lot I highly appreciate your support ,