2 things, IF you were paying attention to BTTF2 you knew about the accident because his parents were talking about it at his house in 2015. Second, It WASN'T the story about Martin that changed him, because he was still talking about being called yellow when talking to Doc the next day when the undertaker was measuring him for a coffin. I think he finally got the message when Doc slips up mentioning that getting upset about being called names caused issues for him in the future, because the race wasn't the first time he ignored being called a coward, it was at the bar when he was trying to get out of the duel with Burford.

I wondered that too, it might have been trial and error, we have no idea how long he had the DeLorean it could have been a couple days and he just returned to a time just after he stole it, it is a time machine. 🤷

Jonathan Yes it changed to Lone Pine Mall AFTER M1 runs over the other pine, and M2 only knew it as Lone pine. In my scenario at the end of the movie when M2 attempts to travel to 1955 he collides with M1 mid temporal transfer annilating both M1 and M2 before they rematerialize in 1955, neither of them make it to 1955, SO M1 never hits the second pine and it becomes Twin Pines restoring the original timline where M1 grows up and the movie restarts.

🤔🤯Time Paradoxes give me a headache! OK, we know from BTTF2 that when you travel to the past it doesn't matter where you start the past is the same and the future only branches off from the point a change is made by a time traveler. Ok, so both Marty from the beginning and end of the first movie are going to the same 1955, AT THE SAME TIME AND PLACE, creating a collision and an infinite dual reality time loop. Here's how it works, M1 travels back to 1955, changes how his parents meet creating M2 who also travels back to 1955 at the same time and place which causes a mid temporal collision which annilates both M1 and M2 along with their DeLoreans just before they rematerialize leaving no evidence in time or space that it ever happened which restores the original timeline where perve George gets hit by Larain's dad, the Twin pines mall is built and M1 is born again to repeat the loop. BAM, 40 year old time paradox SOLVED! ANY HOLES IN MY SOLUTION?