If you need a vector illustration tool but aren't ready for a Creative Cloud subscription, there are powerful, modern alternatives that are safer and more capable than an outdated version of Illustrator:
Available as a one-time purchase with no subscription model.
First, I need to assess the user's actual need. They might be a graphic designer or student who has an old CS4 disc or installer file but lost their legitimate key. Or they might be looking for a free, illegal way to use the software. The phrasing "serial number top" suggests the latter, typical of crack/keygen sites.
If you've lost your serial number, you can try contacting Adobe Support. They might be able to help you recover it.
If you need a vector design tool but want to avoid the risks of pirated software, several excellent legal options exist—ranging from completely free tools to professional alternatives. 1. Inkscape (Free & Open Source)