Ya both need to be offline for it to work H2H....My bro andI have had no issues at all....But make sure you have both successfully tranfered stats at the end before one of you leaves....if one of you is waiting to tranfer stats when the other one has done so and leaves, you're left with a message that the game must end, before yours are sent
Yes you need to re-register
New sight is slightly faster for sending stats to server
There are less games to choose from over at the test site, but there are arcade games you can play/create if you want