Microsoft Certification - 70-764 Administering a SQL Database Infrastructure
Q1: Previously, I have purchased other Microsoft Certification books and have normally got a PDF version, along with the printed book. Is this not the case anymore? Am I missing a disk or something?

On the page you linked to, there were 3 options: book, ebook, and book + ebook. You would need to buy the book + ebook option if you wanted both.

Q2: The book has many URLS for supporting resources, however, these don't appear to be valid any longer. For example, early on within the book, there is a URL given for a list of useful links which accompany the book, I cannot find these online at all.

Yeah, typical problem with dead tree printed versions of the internet: the links are often out of date. You can try using the Wayback Machine at archive.org to see if they've been archived.

Q3: Practice tests also used to come with the book, however this does not appear to be the case any longer. Is this by design? Or am I just missing something here?

On the page you linked to, it says, "This title is also available for sale with a practice test." You would want to click that link and buy the other version with the practice test if that's important to you.