**Q1:** Volume 3 part 1 (a.k.a. volume 3A) has been digitized and reissued as a paperback by Cambridge UP, see <A HREF="https://www.amazon.com/Matrices-Determiniods-3-Part-1/dp/1107414261/ref=olp_product_details?ie=UTF8&me=">Amazon</A>. The digital version is online in the <A HREF="https://catalog.hathitrust.org/Record/000664163?type%5B%5D=author&lookfor%5B%5D=Cullis&bool%5B%5D=AND&type%5B%5D=title&lookfor%5B%5D=%20Matrices%20and%20Determinoids&ft=">HathiTrust digital library</A>, but with limited "search only" access because of copyright restrictions. Quite likely you may find a "pirated" version online, but these would be the legal options.