Top Ten Questions You Want Answered In the Back to the Future Trilogy

Here is the answer: Marty needed a pipe which the store didn't have so the store owner told him about Doc Brown. He warned Marty that Doc Brown is a real nutcase but Marty didn't care. He went to Doc Browns place where he had to solve a difficult code to get in his house. Doc was skeptical at first but Marty seemed to accept him for who he was and Doc offered him a job.

I read somewhere that Marty trespassed into Doc’s home, thought the inventions were cool, and eventually the two became friends. Nice job befriending a trespasser, Emmett.

George and Biff are about the same age and Marty is at least 17. So if Griff is 17 in 2015, Biffs son was born around 1998

He wasn't born yet

I don't think so.

I believe that George DID recognize Marty in the original script. There’s even a theory that suggests it.