So there is .hack/sign .hack/roots .hack/gu in order right? If I want to watch it do I have to start at .hack/sign so I know whats going on when I watch roots? Do all 3 have different stories or something? Is GU a video game?(It looks very nice)

Thats for all now. Please answer my questions and thanks for your time.

Omg I did some search and they also have Legend of Twilight Bracelet, .hack//LIMINALITY.... Which one is the first? >.<