Hello everyone! I'm an absolute newbie on the site... Just signed up.. I'm Andrew from Italy. 
I use RCT3 Soaked&Wild. I ABSOLUTELY LOVE IT ! ! !
....I have a question. I've built a nice park, and I think I'd like to upload it to share it and hear some opinions.
My question is: can I upload the park even if none of the coasters/rides are actually designed by myself? I mean, I've used one or two of the in-game pre-built rides, as well as some rides I had downloaded from the web some years ago.  Can I upload/share the park just the same? If yes, is it required to "credit" the authors of the downloaded rides in my upload description, or not? If so, I'd have two problems: 1) I downloaded those rides quite long ago and I don't even remember from which website they come from  2) In the park, I've renamed a couple of rides, so now I don't even know their original names, making it even harder to trace their origin online.
A few examples: there's a spooky train ride called "Idle Hands"; a thrill ride called "Pagoda Free Fall"; an aquarium called "Atlantis"; a coaster called "Turbokat"... and a couple of other things.
Apart from that, all of the park and the scenario are designed/built by myself from the scratch, so it's an original park.
Thanks in advance!  Andrew

Benvenuto, Andrew!

To answer your question, many parks have been uploaded using downloadable coasters built by other users, and though most of them haven't credited the builders in the description, I've never once seen a builder of one of those coasters complain about that. People who upload content here do it so that other players can enjoy their work in-game, and seeing one of their coasters uploaded in another user's park shows that coaster builder that their work is appreciated. I know I check every large RCT2 park to see if someone has thrown one of my coasters in it, and every now and then, I get the luxury of seeing something I built in someone else's park!

Of course, it wouldn't hurt to credit the builders of downloaded coasters in your parks (at least to the best of your ability), but there's no rule requiring it.

Thank you very much Terry, very helpful!
Andrew