Regarding the ‘Why’ song, Michael Jackson recorded a solo version of it during the ‘HIStory’ album sessions, because that song was a very strong candidate for that album.
But when the track list of that album was being finalized, the ‘Why’ song did not thematically fit to it.
So, on one instance, when 3T visited him in the studio to see him, Michael Jackson played his solo version of it to them in order to get their opinion about it.
3T liked it a lot, and Michael Jackson decided to give the song for their ‘Brotherhood’ album, under one specific condition.
“…So we could have the song [‘Why’], but under one condition: we should keep his voice on it. So we kept the chorus as it was, sang by Michael, and we re-sang the verses… You should hear Michael's version of ‘Why’, that would be cool…” (Tito Joe ‘TJ’ Jackson)
There have been also some other reports that confirm that Michael Jackson recorded a solo version of the 'Why' song when he was working on his ‘HIStory’ album back then.
Also, if you listen to the top quality of Michael Jackson’s vocals on the chorus of the 'Why' song, you can easily deduce that the song was complete as a Michael Jackson’s solo version, right before having its solo verses cut.