Oh, yeah, now I undestand!!!!! (exclamation marks for free!)
These aren't bugs, are the normal game progressions. If you follow walkthrough by reading random lines (or by skipping forward the video) instead of reading from the beginning till the end it's normal you skip some important informations.
Now I I won't tell you how to get through the parts you described. I make you a life example: if you broke your shoes and you are near a shoes store, you enter the store and buy them. But if your shoes aren't broken, surely you don't enter that store, right?!? Or maybe u can enter but with no need to buy them.
The same in the adventure games, do you play some of them before?
Tell me why Rusty have to use the wrench on the pipe with no need? You have to make a previous action to understand why u should do that.
Hope you now understand. If don't, I suggest you to stay away from point&click games, to save money for other important things (like buy a new pair of shoes for example). ;)