GAMMA Questions

Dear GAMMA Users,
I am confused about several problems, hope you can help me.
First is about preparing SRTM for geocoding. 1. I noticed srtm2dem script can help. But it aims at SRTM tiff files as input, can .hgt files as input still use this script? 2. For input files, it should be downloaded from USGS http://gdex.cr.usgs.gov or CGIAR http://srtm.csi.cgiar.org. Can I use 30m resolution dem data downloaded from https://ers.cr.usgs.gov/? 3. What is the datum for my InSAR dem? I guess the datum should be WGS84. Because the srtm2dem script supply correction for the height offset between geoid and WGS84 ellipsoid which can be applied to generate a DEM with heights referenced to the WGS84 ellipsoid.
Second is about preparing ASTER GDEM for geocoding. 1. Because there are no scripts helping to transform the formats of ASTER GDEM. How should I do? 2. I noticed SRTM version 3 and ASTER GDEM version 3 have the same format, same projection(EQA) and the same datum(EGM96). To get correct results, can I use ASTER GDEM tiff file downloaded from https://search.earthdata.nasa.gov as an input of srtm2dem script? 3. By looking through some other answers in the forum, I noticed that dem_trans can help. But now I am using GAMMA-2017 which doesn't conclude this command. Can I get a script of this command? Can this command solve all the problems?
The last question is how to oversample the DEM to approximately fit the resolution of my SAR data.
I have proposed so many questions. So sorry to bring you so much trouble, hope you can help me.
Best wishes,
Helen.