Using Cubase 5 with Cubase 8 Artist license

Hi guys,this is my first post.
I tried to find an answer searching in the forum but nothing helped me.
I’ve recently bought Cubase 8 Artist and i would like to use Cubase 5 too because i know(or i hope) that with a newer version i can use the previous ones.
I’ve asked Steinnberg and they gave me a link to download Cubase 5.5.0 but,after i’ve installed it,asked me for activation.
Thanks to everyone