SimPort

Just one quick question. Is there a way for me to use SimPort with unregistered game? Yeah Im aware that you should be connected to their website, but I dont know maybe there is. Because my sim wishes to host a show on a venue.

Unfortunately, no. But there is a cheap solution for it. Buy from a store any original old Stuff Pack (they usually go for 10 euros or so) and just register on the site using the code. You'll be able to use Sim Port then.

Gotta be honest I brought the Sims off steam when it was 66% off, didnt realise any pack would had unlocked it though

Yes, in order to register in TheSims3 community and site, all you need is a code of ANY expansion/stuff pack or the base game. Of course altogether with the forum registration, you'll be able to use Sim Port as well.