Nope, he told me I need to activate it on Stardock site, but I also checked Steam and it can't be activated there.

There should be a settings option to show beta releases. Look for it and enable to see the FE beta.

Yes, they've said many times that the codes to unlock games in Stardock are tied to an individuals account.  That's why so many people have problems when they start a nnew account and don't ask to have their accounts merged.  I don't know if Stardock will transfer his code to your account but he'd probably need to initiate the conversation since it's his code.