[Sugar Cube] Multiple items to unlock thing?

I've been trying to figure it out myself but I've been unable to work it out.

I'm trying to set it so that you collect multiple items (hidden that is) when you go to certain passages/areas and you need all of them in order to unlock a new route.
Think of it that you need to collect multiple keys to unlock a huge door.

I know how to set if/then codes and such (sorry if I'm using the wrong terminology my mind isn't great).

Is it possibly to set the coding so you need multiple items to go to a certain passage and continue down that storyline.

ALSO: I was trying to search earlier, but how do you set a "main menu" for your game? Like create one that shows your saves or the credits.

Thank you and please mention if I need to be clearer or if you don't understand (I have a bad time explaining things sorry).