Thank you for your answer. About Camelot, I did try to use a walkthrough and the manual, but without success, since you have to answer ALL the riddles you’re receiving, and they seem not to be random. I haven’t use one of the Gamefaqs solutions which seem to have more riddle answers, so I’ll see if that could be a help.
Anyway, I’m more concerned about Codename: Iceman. I’ve tried to use several walkthroughs and the game manual in this case too, many times, but couldn’t pass the submarine part. So if someone has a saved game after this part, it would be a great help for me.