The original iMac was the G3 which came out in (1998). It was followed by the G4 (2002), then the G5 (2004), then the Intel iMac plastic version (2006). The 5th iMac was the aluminum iMac which came out in (August 2007), followed by the iMac Aluminum Unibody (2009). The newest iMac is simply called 2012 iMac and it came out on November 30, 2012.
Apple no longer sells a 20" iMac. They sell a 21.5" and 27" iMac. Both come in aluminum.
iMac's do not come with night vision.
The iMac was invented and went on sale in 1998. The iMac as it looks today was introduced in 2006.
1998
The 2011 iMac comes preloaded with the iLife software bundle, which includes GarageBand.
You have to purchase Photoshop separately.
The 2011 iMac does not come with a 3.0 USB port. It has four 2.0 USB ports. The new 2012 iMac does have four 3.0 ports.
No, the iMac does not come preloaded with Office. You can however get a great free office program called Open Office or Libre Office.
Who told you it had no USB ports? Of course it has USB ports. The iMac has 4 USB ports, 1 Firewire port, 1 Thunderbolt port (2 on the 27" iMac), 1 Ethernet port.
The iMac doesn't come with a built-in uninstaller, like the Windows system does. However, you do not need special software to uninstall programs on an iMac. It's as simple as dragging the program over to the trash can and emptying it.
The current iMacs only come in one color, if you are looking for previous models of the iMac, I would suggest looking on the Wikipedia page for the "History of iMacs".
An iMac does not come with photography programs already installed. There are, however, programs available to download free of charge, or to purchase. The free programs are good, but if you are a photography whiz/fanatic, you may need the purchased program.