I can only comment on this last question. I believe that there is at least one Enrico Caruso side that has remained in print since it was first issued by Victor sometime prior to 1921.
Undoubtedly, Caruso's 1907 "Vesti la giubba" has been continuously in print since its first releases on Victor 88061 and HMV 052159.
Mike -- mrichter@xxxxxxx http://www.mrichter.com/