Can a vesa mount be used on an early 2008 iMac

Hi, can anyone help please?

I have an early 2008 20” iMac which I need to use to run an older piece of vinyl cutting equipment software. I have to use this iMac because the software will not run on any of my newer iMacs.

I’ve had a bit of a studio reshuffle and where I want to site the 2008 iMac it would be really useful if I could have it on a flexible arm.

I managed to obtain a visa mount adapter for iMacs but can’t seem to use the ‘card’ trick to release the stand in order to remove it and install the visa mount adapter? 

Can anyone tell me if (a) this is actually possible on a 2008 iMac, and (b) if it is, any suggestions as to how to go about it?

Finally, if it’s not possible on a 2008 20” iMac, which of the early 21.5 inch iMacs can take a visa mount as I may be able to run my software on one of these if I can find one? However, I would prefer to use the current 2008 iMac if I can as it runs perfectly.

Thanks In advance.

Jon.