You don't need to tell me you've "given up", you just need to not bother to reply
Because they inform each other. One shows him "grabbing" the collar, but the other shows that he wasn't actually grabbing the collar, he was grabbing the neck and the collar came with. You can send someone off if a second angle informs on the first.
No.
The rules for violent conduct when it comes to the head/face are much lower bar, the contact only has to not be negligible. Nobody is suggesting Casemiro was trying to kill Hughes Homer Simpson style, but that's not the bar for a red card.