I'm testing the install on both 2012 server and 2012 R2 (both RTM) and I couldn't install .net 3.5 without giving the installer two separate sxs folder based on server version. I added a folder sxs\2k12 and sxs\2K12R2 in the prerequisites folder and added code to check for version and use the appropriate folder in the .net install function.
Comments: ** Comment from web user: SpRambler **
Comments: ** Comment from web user: SpRambler **
of course each sxs folder was copied from the appropriate source iso. sxs2k12 from the 2K12 rtm iso and sxs2k12R2 from the 2K12R2 iso. I saw both folders have the same size and the same number of files but all I know is that the install does not work if I specify one single folder.