I don't know why this happens (yet) but sometimes backups do not restore on BlackBerry 10 (BB10) via BlackBerry Link (Link). I've had two distinct symptoms - one is the restore process getting stuck at some percentage - for me it was 2%. The other was the device rebooting in the middle of the backup and then Link failing to detect it. The latter produces an error message "Backup did not complete" with explanation "There could have been a problem with the device or connection during the backup. Verify that the device is turned on and connected."
What I've found is that if you cancel the stuck restore from the device (you don't need to cancel in case the backup failed), then just retry the restore, the second attempt succeeds. As far as I can tell the resulting restore works as expected.
So there you have it, if you restore gets stuck or fails, retry.
The first thing you will notice about your Messages box is that it grows rapidly with stuff not pertaining to you. Probably most of those messages are not for you anyway but part of a mailing list you were forcibly added to. The thing you want to do is just - Mark All Read. But it is not there. Actually it is there but it isn't called exactly that and it isn't visible at all times. In order to mark all messages as read - follow these steps:
As you probably figured out, you can use this maneuver to mark messages read prior to any date.