Adobe no longer supports CS2, CS3, or CS4. They released official serial numbers for those. However, Adobe has never legally abandoned CS6. Using a repack is still illegal.
You want After Effects CS6 specifically. Here is how to get it legally, often for free or very cheap. adobe after effect cs6 repack
Before we discuss the "repack," we must understand why there is demand for an 11-year-old application. Adobe After Effects CS6 was the last perpetual license version. You bought it once, and it was yours forever. Adobe no longer supports CS2, CS3, or CS4
Users seek the CS6 repack for three main reasons: Adobe no longer supports CS2