Most of the v4 tips should be in your instruction manual. I do not have a v4 yet, so I can't give you any helpful hints about it, but you might wanna take a look at this link for some shop codes. Here's what I DO know about the v4, though: If you are asking other TamaTalk members for passwords that allow you to get items, you would have to have the same tamagotchi username as the person who tries to give you a password, or else it won't work on your tama. Hope I helped!
I don't know any codes of my own since i'm sure my v4's user is different from urs ... but these links might help ... they include growth charts too if u want