upgrading a mid 2011 (IMAC) to 10.6 is it possible?

i have a iMac mid 2011 originally (operating system) is 10.6.6 but now its working with OS X 10.8 Mountain lion and i want to downgrad it to snow leopard.

i want somebody to help me solving this biiiiiig problem.

somefriend told me that it is impossible.

but i now it's originally bought with an 10.6 DVD. so it could be downgrade

is there any special methods that could help ?

please could you help me?

i read something in the internet about cloning an internal hard drive working with snowleopard into an external HDD.

But really i need someone that could teach me how??? with a good explanation

am waiting for your opinion and ideas.

i would be very thankful

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