Downgrade to Lion from Mountain Lion OS One of my friend bought his MacBook Pro with preinstalled Mac OS X Lion (10.7.2). Afterwards, he installed the Mountain Lion (10.8) developer preview in it.

He wants to downgrade the OS to Lion (10.7). One option I see is using the Lion recovery suggested at http://support.apple.com/kb/HT4718. 

But, he had not purchased Lion before as it was preinstalled on his MacBook Pro. Does he need to purchase Lion now from the App Store while in the recovery mode OR if he doesn't have to buy it, will he get it free?
That's why they say not to install the Developers Preview on your daily machine (as only OS...)

Nevertheless, not having the a Lion disk isn't a obstacle. You should do fine with a decent backup and Lion Recovery Disk Assistance.
If you follow these 7 easy steps, your friend will have his Lion back in no-time.