to install mountain lion do i need lion?

Go to the top left, and click the Apple logo. Choose About This Mac. Write down the Processor info. Mine is a 3.33 GHz. 6-Core Intel Xeon (which I know is the Westmere series). Now click on More Info.

The System Profiler will open. At the very top, you'll see Model Identifier as the second entry. As an example, mine says MacPro5,1 .

If I enter that here, the resulting page tells me everything about that model, including when it was built. Because a lot of Mac Pros fall under the 5,1 heading, I know to scroll down to 6-Core 2010 Westmere from the About This Mac info of my CPU. So my particular Mac was made sometime after July 27, 2010, making it a mid 2010 model.

Using the same procedure, you can narrow down when your iMac was made.

The best test that you can do is to go on the Mac AppStore and try to buy Mountain Lion. Directly after double-click on the button I get:

"We could not complete your purchase. OS X Mountain Lion is not compatible with this computer."

I have a Macbook 4,1. If you want to upgrade on Lion now ... you are in the same boat than me. I just got an answer today: https://discussions.apple.com/thread/4188465?answerId=19201878022#19201878022&ac_cid=op123456#19201878

I can upgrade from 10.6.8

How do I request a free copy of Mountain Lion?😕

Even if your Mac was eligible for a free upgrade, there was a time limit to request it, and that is long past.