The Level 9 items puzzle is a hallmark of this type of game and indicative of similar puzzles you'd have found in Dungeon Master, Eye of the Beholder etc. As a kid I'd spend days scratching my head trying to figure them out.
These days after an hour or two I lose patience and have a quick google for the answers.
The other gameplay mechanics mentioned are also typical of the genre - you want to explore everywhere and keep an eye out on every wall for buttons etc leading to secrets.
Yeah I guess you're right, I can't really remember much of the games back then. I do remember them being pretty hard sometimes but I couldn't remember anything like the level 9 puzzle, maybe as you say due to the times we'd just Google after a while
