Warning Beacon

I'm just going to throw a few thoughts out there. This is all conjecture and speculation as I have not seen the movie and will not know the answers till June 8th like the rest of you. So here goes... There seems to be a big argument as to what planet this all takes place on. LV223 or LV426? If it's LV223 then where is the connection to ALIEN given that Nostromo set down on LV426. You can clearly see imagery on the bridge of Prometheus that says LV223. But does that actually mean they landed there? Or was that simply a scan of the system they were entering? And how about those Engineers? I'm thinking we are seeing the last of them! How long ago did they seed Earth? And they never came back to see what came of it? They don't strike me as being very stealthy. Is it possible that they created something that got the best of them? A distant cousin of the Xeno? We know Prometheus sets a collision course with the Juggernaut to keep it from taking off. The remaining crew are left stranded. Now think about this, the tagline says THE SEARCH FOR OUR BEGINNING MAY LEAD TO OUR END. That implies that the juggernaut was most likely leaving for Earth and the Prometheus crew considered it a big enough threat to destroy their own ship and strand themselves on an alien world. How many years pass between Prometheus and Alien? The engineers are obviously far more advanced then humans so I'm sure they have cellphones. How come another juggernaut was not dispatched to Earth to finish the job. Why? Because with the crashing of the juggernaut they became extinct! And the icing on the cake... the signal that Nostromo intercepted was a WARNING not a distress beacon. Let's just say for arguments sake that the derelict in Alien is NOT the same ship from Prometheus. Why would it be sending a warning in a language that Humans could understand? It would either be sending a distress to it's own people that we surely would never be able to decipher (this ain't Star Trek and we don't possess universal translators!) or it would be sending an invitation to us so that we would stumble upon it's cargo. So this leads me to believe that the Juggernaut in Prometheus is indeed crashing on LV426, it IS the derelict we see in Alien and the surviving crew members of Prometheus are responsible for the warning beacon in Alien. Surely the company would have a contingency plan if the Prometheus did not report back. Seems to me the crew would do everything possible to warn others, including the company, away. They would likely choose to sacrifice themselves instead of risking a rescue mission and possibly taking any infections back to Earth. Thoughts? These are just some ideas,theories,etc. There's no need to get hateful if you disagree. It's just for discussion.