Question: How did The Green Goblin get captured and sent to Ravencroft after he killed Gwen?
Question: The is something that I didn't understand in the movie. Spiderman killed Electro, which is something completely out of character. What was Marc Webb thinking?
Answer: Peter didn't set out to kill Electro, but he has to stop him somehow. Overloading him is pretty much all Peter has to work with in terms of stopping Electro's rampage. He doesn't know what effect it will have on his opponent, but he hopes that it will serve to stop him in his tracks, which it does. Had Peter set out with the specific intention of killing Max, that would indeed have been wildly out of character, but he didn't - he simply did what he had to do to stop him. It's unlikely that Max is actually dead anyway; it's well known that Sony intend to bring the Sinister Six into play in upcoming movies and Electro has been a key member of most incarnations of that team, making it highly likely that he'll be back.
Question: Why wasn't Chris Cooper credited for his role as Norman Osborn?
Answer: Cooper's role was a cameo. And often, when well-known or well-respected actors appear in surprise cameo roles like this, they go uncredited. Usually to either try to maintain the element of surprise, or try not to overshadow the rest of the cast.
Question: How did Spider-Man alert Gwen's family and friends of her death without being accused of killing her?
Answer: Peter could have contacted the police anonymously.
Question: Who is in charge of Oscorp now?
Answer: Donald Menken, the Vice President of Oscorp, framed Harry for covering up Max Dillon's accident and has him removed so he could take over the company. By the end of the movie, Oscorp would now be under his control.
But he was killed in a deleted scene.
Deleted scenes don't make for canon content - it has to involve a degree of guesswork. Some deleted scenes happen, we just didn't see them in the movie, others are movie ideas that were cut out precisely because they don't fit the movie as released, so didn't happen. No way to know which is which, and this is just a thought exercise anyway.
So this is possible that, at the end of this movie, Menken is still alive, right?
Question: How come they stopped with this movie and didn't make any more?
Answer: There's a plethora of reasons, as others have said. This film had a relatively large budget (projected between $200-$290 million depending on the source), but was the lowest-grossing film of the franchise, bringing in only about $700 million worldwide when it was expected to be a potential billion-dollar film. Critical reception was lukewarm at best, and fan-reception was very mixed, whereas most of the previous films were received very positively. (Even "Spider-Man 3" fared better in general with critics and fans.) Andrew Garfield was having issues with the studio and executives, and rumor has it that he was possibly going to be fired after showing signs of disrespect towards Sony. (In part because Garfield had serious issues with them for interfering with the production of both "Amazing Spider-Man" films and making demands/undermining the story to set-up future films.) There were already a lot of issues building up behind the scenes because Sony was hoping to use this film to set up about a half-dozen more sequels and spin-offs, and they panicked when it wasn't the huge hit they hoped for. Finally, talks began with Marvel/Disney after its release, and Sony opted to reboot and "share" the character with Disney so Spidey could join the MCU.
Answer: Reviews and box office returns weren't up to studio expectations. In addition, the director and Andrew Garfield both expressed not wanting to return to the series. Those, combined with talks to Marvel, resulted in the franchise stalling.
Answer: Actually, the timeline is a bit more muddled, since serious talks with Marvel and Disney about the rights to Spider-Man didn't really take off until after this movie bellyflopped at the box office. That's when Marvel offered them the shared custody that ultimately resorted in Spider-Man:Homecoming, where it's Marvel that has the final say in the creative process.
Question: Are there any plans to release a director's cut?
Answer: At the moment, no. Given the fact the series was rebooted, Sony seems to be putting its focus on the new films. Although given that an alternative cut of 2007's "Spider-Man 3" was recently released, it's possible a director's cut might appear in the future. But at the moment, there are no plans for one.
Answer: Peter could have webbed him up and called the police anonymously.
MasterOfAll
Very likely. However, there was a deleted scene in which Peter, out of anger over Gwen's death, almost beats Harry to death.
Yes. We also see Goblin getting knocked out when all hell breaks loose, and the gears all break apart. Chances are, Peter just webbed him up. (Although, as the other response says, he also got beaten up in a deleted scene.)
TedStixon