I can share what I know as a former cubicle slave at MSFT.
For MS, there is a standard IT build that contains versions of Windows, Office, Defender, group policy, remote access, etc. The IT desk and IT remote help people support this standard build.
Prior to Win10, the policy was 2 IT builds pushed out per year. This is much higher than the industry standard.
Employees can pretty much download any software they want. They should go to the site license website and download stuff like Adobe reader from there rather than from random websites, but I certainly did both and never got called on it. MSFT respects software IP and expects employees to do the same. If employees try to download stuff that doesn’t pass corporate security, it will be blocked. Dodgy or NSFW websites will get you an automated email (and might also be sent to your manager but I’m not sure if that happens or if it has to happen a lot before the manager gets an email).
Net net, it’s pretty standard with the focus on security and outside hack avoidance. Because testing software before release is a really big deal, it is really encouraged that employees dog food software but don’t have to. Some groups get “named and shamed” by releasing the use levels by department. Given that most employees are interested in software, a big chunk are happy and eager to run dog food even though that usually means about once per year your machine crashes and has to be reimaged as part of the testing process. In my experience, it was the A type manager that didn’t really understand the business and couldn’t be bothered to install their own software, were the dinosaurs running the oldest software possible while loudly complaining that “they were way to busy and critical to MSFT to be at risk of dog fooding new product.”
Now with Windows 10, the internal ms folks get the Windows 10 enterprise version pushed out.
There are numerous “dog food” sites that MS full time employees can and do sign up for. Opt in process. Windows, Office, SharePoint are the pretty common ones. these are “beta” versions of pre release software. And then there are the alpha versions that certain groups like the Windows developers join.
So, at any one time, there are multiple versions of alpha users, the dog fooders, and (usually IMHO a bunch of narcissist jerkwads that only run market release software.