>>303322792
I think green squares are somewhat unreliable/buggy, i remember having issues with them as well. As for searching through levels: after beating game once you'll be able to level select, so you can pick up unlockables you've forgot on your way. iirc you'll even have access to the list of how much shit you still have to find on each level. So, if it's your first playthrough, just enjoy the story and go through levels without putting too much effort into completionism, game is designed in a way to let you easily get everything after beating it.