No! Earlier versions of EQ do NOT need to be installed before installing EQ7 Upgrade. If you install EQ7 Upgrade on a new computer, simply start with the EQ7 Upgrade CD. The installation will ask you to input the EQ6 license ID and EQ6 password and then it will ask for your EQ7 license ID and EQ7 password.
Yes. You can uninstall EQ5 and EQ6 at any time. It will not affect EQ7 Upgrade.
Nothing you made and saved will get uninstalled. Everything will still be on the hard drive in these folders:
Your EQ5 and EQ6 projects will still be on the hard drive here:
Your My Library files will still be on the hard drive here: