Is there a Windows 8 Full Retail version available for download? I have checked Mircosoft's site several times and it only directs me to the Upgrade version for download only. I ask because they would be installed on machines with no optical drives. I'm talking about legitimate downloads right from Microsoft, btw.
I don't believe there is, no. However, you could buy a retail disc and use a friends pc to make a disc image and then flash that to a usb stick. From there you could install it on one pc using the code that came with the disc. In order to install it on more systems you would have to purchase the activation keys from Microsoft on a per machine basis.
I don't believe so - the only digital option available at the moment appears to be the upgrade versions. They're essentially the same thing they just check for a key in your bios before installing, and require you to input the key if there isn't one before proceeding with the installation.
Using the method I mentioned above and using a retail disc image would allow you to fully install it without activating it. From there, go to the start screen and type "windows activation" to bring up the activation dialogue. You can buy a key with a credit card.
No prob. If you don't want to go through the hassle of using a friends pc and making a bootable usb flash drive, you could always pick up an external disc drive for about $50 - you could even return it when you're done with it, just keep the packaging. Remember though that the install is about 10x slower using an optical disc than using a flash drive.