There are countless forum threads complaining that Malwarebytes 4.x blocked legitimate software, broke network drives, or flagged false positives on system files. Version 3.8.3 has a reputation for being less aggressive and more predictable.
A: Officially, no. Unofficially, you can search for sealed retail boxes from 2013 (e.g., on auction sites). These are rare and expensive.
A: It will install and run with some tweaks (compatibility mode Windows 8), but Microsoft does not guarantee stability. Expect occasional UI glitches.