On July the 10th you described 12.37km at 4:51 min/km average as a hard run. It might perhaps be, if you are more fast twitch, that you can rattle off fast 400s. But I don't believe it possible to go from that level of fitness in July to a sub 3 hour marathon in early 2021, never mind anything close to what you are aiming for. Here's a challenge: I suspect you would struggle to run 15km in an hour at the moment. Why don't you try it? An hour's tempo run (not race-like effort, it should be very controlled) is standard marathon training. You might just manage it, but I very much doubt by much. In which case it will be enough of a challenge for you to try to break 3 hours in early 2021, and we can cut out the delusional stuff coming from JS.