**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. 

With some further search I actually found a library in India that has placed the digital version <A HREF="https://archive.org/details/in.ernet.dli.2015.74887">online</A> (a 54 MB download). Quite possibly not fully legal, but in the spirit of the <A HREF="http://blog.archive.org/2020/03/24/announcing-a-national-emergency-library-to-provide-digitized-books-to-students-and-the-public/?iax=ntlemrlib%7ctxtlnk">National Emergency Library</A> I guess in these times a download can be justified.