Remarkable memories here
as far as I can tell
1965 - Demo backing track for ‘No Greater Love’ produced by Harvey Fuqua.
Just a piano and organ recorded no backing vocals and of course this would go on to have additional overdubs added to the Marvin version for his posthumous LP Motown Remembers Marvin Gaye
1966 - The above 4 released recordings with Mike Valvano and R. Dean Taylor.
No hint that there are any additional vocals from those you mentioned.
1967 - Re-recording of ‘It’s My Time’ - anyone know the musicians?
1968 - 2 other unreleased recordings; ‘Masquerade’ and ‘Fantasy’.
Neither Masquerade nor Fantasy got beyond instrumentals there are no backing or lead vocals - that appears to be the lot for the Mynah's at Motown with all four tracks being released and both versions of It's My Time which was also covered by the Underdogs and Messngers