The background vocals for "The Girl Is Mine" - the adlibs at the end of the song - are most probably from 1982, vocals that were not released then, as his voice seems to be truly young and similar to the rest of the vocals in the song.
As for the vocals in "For All Time", I compared the demo and the 2008 release and they are not new either, except for the last chorus, partially, in which he provides fresh background vocals to it. Not even the bridge is new, it is only technologically improved, as the rest of the song and instruments, and I believe there may be some fresh background falsetto vocals in it - as in cleared, because on the demo version, it could not be very well heard - , but the lyrics are the same in there as well. It is an incredible song, in my opinion.