magic keyboard won't connect to my iMac 2012

This is what they said to me at the Apple shop, but I was wondering if there was a way of connecting to the bluetooth.

Is it the Magic Keyboard without number keys, (yes it is)if so it needs MacOS 11.3 or later.

It does work on Bluetooth with a compatible iMac running a compatible version of macOS. Neither of which you have.

IF EVERYTHING WAS COMPATIBLE, MY PROBLEM WOULD NOT EXIST.

I cannot update to modern versions because the new versions do not accept my applications and I cannot buy new applications at £600 each every time that Apple makes an update

The keyboard comes with a cable (it is the same cable that one would use to charge a mobile phone). My iMac was bought in 2012 hence why it does not have a USBC connection, therefore I got myself a suitable cable. Bluetooth connected just for a few seconds and then it disconnected again. I tried to connect and disconnect Bluetooth as well as the computer several times. The magic keyboard appeared on the window a couple of times to be paired but it did not. Then it stopped appearing.

My question is the following.

My computer macOS Sierra 10.12.6 cannot be updated because I have appliances that would not work with a newer versions. Apple says that this is the reason why it won't work, but I cannot understand that if my computer's bluetooth works perfectly well with other appliances, why it does not work with the magic keyboard.

Besides, the magic keyboard works as long as the cable is connected to the port but I find it utterly ridiculous that I paid £99 for a wireless appliance that cannot work wireless.

Apple produces excellent material but it is terribly expensive. Why do they keep on changing sockets and connection cables?

Capitalism at its full. NOT RIGHT

It is wireless but to connect to the bluetooth one must use a cable. For some reason it does not connect.

yes, this is the theory but it does not connect.

yes, but after 4 months they stop working