Question: So I have a very nice 27" 5K iMac, late 2014 model.  

It runs Big Sur, but it doesn't get the Monterey upgrade, because it is 1 generation too old.

[I believe I can get Monterey to work using OCLP](https://github.com/dortania/Opencore-Legacy-Patcher/releases) on this hardware, but I rather don't want to mess with that as that would require a full re-install, for which I have no time. (A lot of home-brew/custom software that would need to be setup fresh.)

So I wonder if I can run Monterey in a VM instead, even though the underlying hardware is officially not supported.  

(I've got 24 GB RAM to play with. Plenty for a VM.)

I can just give it a try off course, but Monterey is a big download and I have very limited bandwidth at the moment, that is also needed for other stuff during the day.  

I rather not download the whole thing over several nights to find that it doesn't work.

Can anyone confirm whether this would work or not?

Answer: 
I have macOS Monterey version 12.1 installed on a VMware Fusion Player virtual machine on a iMac (21.5-inch, Late 2013) host. The iMac is running macOS Catalina version 10.15.7 from a 5 Gb/s USB port. The USB drive is a 500 GB Samsung T7 SSD. The VMware Fusion Player is the free for personal use version 12.1.2.

I created a Monterey installer drive by using a Big Sur virtual machine. I following Apple's instructions: [How to create a bootable installer for macOS](https://support.apple.com/en-us/HT201372). Instead of using a USB flash drive, I created and used a second SATA drive for the installer.

The virtual machine has 2 processor cores and 4096 MB of memory out of the 4 processor cores and 16 GB of memory installed in the iMac. This is a custom virtual machine where macOS 11.0 was selected as the operating system.
Yes, that should be fully possible. Note that there will be some performance loss - depending a lot on what type of computing you want to do. For example it might not be a good experience for 3D gaming, but will probably work just fine for app development.