Yes, your Xbox Live membership travels with the account, not the console. So if you have a Gold Account signed into a console, you have Gold privileges on that console. You can recover that account on a different console and have Gold privileges.
This is also covered in the Gold Family Pack FAQ.
Q: I have multiple consoles in my family. Does my Xbox LIVE Gold Family Pack have to reside only one of those consoles?
A: When an individual is added to an Xbox LIVE Gold Family Pack, that person’s Xbox LIVE account must be on the same console as the primary account holder. However, once they are a part of your Xbox LIVE Gold Family Pack, that person could recover their account on a different console and still remain a part of the Family Pack, as long as they reside in the same country as the primary account holder.
I'm also in the dashboard preview. I've had a similar issue since early November, but I don't know if it's exactly the same. It comes and goes.
- I can send messages to other people, (party and game invites, for instance) and they get them, but trying to respond to them just times out.
- If other people send messages to me, I can't receive them. If I log out and log back into Xbox Live from the Xbox menu, then I'll get a flood of messages all at once.
If I manage to get one of these messages, and the lobby or party is still open, I can join the lobby/party. Usually when I've identified that this is the problem, I'll ask my friends to start a lobby and send me a combo party/game invite, and then I'll quickly log out and back in, and accept the invite.
Sometimes this happens in reverse (ie, I'm the one who can get messages that I can't respond to), and the workaround is reversed. It requires a decent amount of patience when this happens in order to get to play with my friends.
If this isn't your issue, or it doesn't solve it, you'll want to talk to Microsoft via the Connect Dashboard. You should have access to this page if you're in the dashboard preview. From previous experience, I don't think they're able to roll back your dashboard revision, but you might find a solution or workaround, and at the very least, we're helping everyone else avoid this issue when the update goes live.
Best Answer
The easy way to tell the age of your Xbox Live account is by viewing your Gamercard from the Xbox Guide.
You can view this info on any of your friends' (or recent players') Xbox Live profiles as well.
As far as the 10th year anniversary promotion goes, they are sending these out to people who have been Gold members since the beta, so unless your number reads 10, you're unlikely to get one :)
The sweepstakes, on the other hand, is open to everyone with Xbox Live. Just download the gamer pic to enter. Further, you can get a second entry if you're a member of Xbox Live Rewards, which is free and has other monetary benefits.