I don't see any indication in "Q Who?" that the Borg wouldn't already know all about Earth and the Earthlings.
Nor do I see any indication in "Regeneration" that the Borg message sent towards the Delta Quadrant would have been of much significance. It probably made the Collective aware of how the mission went the first time around - but since the Borg can time travel, they could time travel until they reached the desired outcome, which indicates that the history that unfolded after the ST:FC end credits rolled is the one that the Borg desired.
Indeed, ST:FC looks like a time loop to me. In the first iteration, Zephram Cochrane is a crazy hillbilly who happens to have some fundamentally faulty ideas about warp drive, and the Borg help him invent warp at the crucial moment by bringing him help from the future. In the last iteration, Cochrane has got it almost right, and the future helpers only need to do a little bit of tinkering to create "the engine they read about in the history books". Thus, the last iteration was always part of "the timeline", whereas the earlier iterations were part of different timelines where at first the UFP didn't exist, then something like it began to exist but with really poor warp drives and tech, and finally the UFP we know began to exist and enjoyed high standard Cochrane warp engines from the very start...