Apple Keyboard Not Recognized by Winodows

I also have an old Apple Keyboard, model A1314. This was recognized as an Apple Keyboard immediately and all keys function properly. The "Keyboard" tab finally appeared in the Boot Camp Control Panel as well.

Nice. It proves what I suspected. The newer MK2 requires the drivers that are considered SPI-compatible (Serial Peripheral Interface). A 2012 Mac does not have any SPI drivers for Windows, hence your problem.

Unfortunately, I need to use the newer keyboard with the numeric keypad for majority of my work!

It should still work, if it is connected via a Wired connection. However, you may be able to use Windows-generic BT drivers. The issues that comes up when you switch to generic drivers is that the special Function Keys will not work.

Yes, the newer Keyboard works fine on MacOS

Nice. There is a USB version of the same Keyboard, which may be a better choice for your 2012 Mac.

• A1243 Apple USB Keyboard - Apple-Aluminum-Keyboard-MB110LL-Refurbished
• Belkin YourType Bluetooth Wireless Keypad - Apple

The Keyboard works through both wired and Bluetooth connections, however the special Function Keys do not.

Using either Fn+ the key and without it.

Could you just clarify, are the Function Keys supposed to work through a wired connection?

Yes, they are, but it is dependent on the driver.

Or is my only option to purchase the actual USB version of this keyboard?

No.

First, let us try the simpler solutions. Does a SMC Reset (How to reset the System Management Controller (SMC) on your Mac - Apple Support) change the behavior using the Wired/Wireless connection?

What is the year/model of your Mac (do not post the serial number) and macOS version?

What is the Keyboard Model? Based on Wired+BT mentioned, it seems to a Wireless MK2.

In Windows Device Manager, do you have any unknown Devices?

As a test, if you have another older BT Keyboard, can you pair it and test?

I assume the keyboard works fine on the macOS side? Since you are running High Sierra, the macOS side has newer drivers than the Windows side.

Does the Keyboard show up properly when you connect it via USB?

Can you check if you have any Apple drivers in Windows Device Manager for HID (Human Interface Devices)?