Versions prior to CS6 (e.g., Illustrator 10, 9) are considered abandonware, but Adobe still holds the copyright. Downloading them from abandonware sites is technically illegal and unsafe.
While Adobe no longer offers its classic software for free, there are legal ways to access older versions of Illustrator—primarily for opening legacy files or learning the interface. Here is what you need to know. free old version of adobe illustrator
Beware of websites offering "free standalone installers" for Illustrator CS2, CS3, or CS4. Adobe has retired the activation servers for these products, but they only provide installers to existing license holders . Downloading them without a serial number is software piracy. Versions prior to CS6 (e