Spiderman from the Raimi movies is a different person than the Spiderman from the Amazing Spiderman movies, who is a different character from the MCU, who is a different character than the Spiderman from the 60’s show, who is a different character than … So no, we don’t know his backstory and it’s weird that Tony Stark suddenly visits a teenager who we never seen before and asks him to help him.
Black Panther - before seeing the trailer I didn’t even know such a superhero exists. After seeing the movie I know he exists and he’s from some fake African country. I know nothing about him as a person and nothing about him as a superhero.
Bucky - you didn’t understand what I was trying to say. Sure, they were friends. What I was trying to say is that in my opinion Steve Rogers had no real reason to chose a guy who is a known mass murderer over people who he knows are actually good, it goes strictly against the character which was shown in the previous movies.
Just to be sure - I have never read any of the comic books, I am judging the characters only from what I’ve seen in the previous MCU movies.