The wireless keyboard is not backlit that comes with an iMac but you can buy a backlit keyboard.
The iMac
There is no apple key on a newer iMac.
The iMac is an Apple computer.
Older iMacs use a USB keyboard which plugs into a USB socket on the back. Some newer iMacs use a Bluetooth wireless keyboard. These need to be turned on by the switch at the right hand end. A light indicates if the keyboard is working. If the light flashes it means that the keyboard has not yet connected to the computer. (See links below)
Alt is Option on the Mac keyboard.
First off the keyboard must be a Bluetooth keyboard such as an Apple Buletooth keyboard. Secondly you must have Bluetooth turned on and it must be discoverable. To turn it on and make it discoverable click System Preferences in the Dock and then choose Bluetooth from the screen that comes up. There you will see ON & Discoverable. Click each box and then close out the screen. Turn on your Bluetooth keyboard and it will pair with your iMac.
Yes you can connect your wireless and USB iMac keyboard to PC or other iMac's. If you want to know how there are some videos on YouTube to help you do this.
There is none on the keyboard.
No, the iMac is not a touch screen. The only touch screen products made by Apple are the iPad, iPhone and iPod Touch.
The Apple iMac is a computer and its purpose is to compute.
You do not make the iMac, Apple does.