HI3 is your current trip. Actually people normally ask "do you have an HI-3" on a current trip. HSS is for a different or future trip.
The HI-3 is the same as an HSS. The HSS can be used to see anyone's trip. Buddy says he's flying flight XYZ? You can look at the NS, fund the sequence number(HSS), and use the HSS entry to see what he's flying.
Hotel and transportation info is on the hotel info or HIHTL code.