I don't know. It seems pretty straightforward to me. Click on the big red button.
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Where did you come up with all those versions? There is no Google version to download anymore. Although you could still download the pro version of SU8, they have made it so you have to search a little. It's not a difficult search but they do want you to use the currently supported version which is easy to understand.
As to the admin thing for installing, don't blame the software. That's coming from the OS. The software doesn't require you to have administrative privileges but the OS is trying to protect your computer from you and others who might be interested in doing bad things to it. If you are using Windows XP, there's no need for the administrative privileges because the OS doesn't care.