do you mean reverse the scrolling back to how it was in OS X Snow leopard?
go to system preferences > trackpad > scroll & zoom > scroll direction
change the setting from natural scrolling to reverse scrolling
install os x lion
Mac OS X Lion is version 10.7
It is probably going to come out after OS Snow Leopard
Yes, you can upgrade to Lion from any iMac that uses the Intel processor. But the newest OS is Mountain Lion.
There are alot more touch gestures in lion as well as mission control and easier scrolling
If the computer is running Mac OS Lion or higher we recommend the 2011 version.
Mac OS 10.6
Mac OS X 10.7 (Lion) was created by a team of programmers at Apple.
Lion is due for general release in July 2011.
there is an awesome video on apple.com
yes
Apple's Mac OS X. OS X Lion OS X Panther OS X Leopard etc.