There's no law that states you can't. As a player, you just have to be careful. You see goalkeepers doing it all the time, that is merely to protect themselves from a late challenge. For me, photo number 2 is fine, he's using his knee to gain height. The bottom left photo, his knee appears to be going into the back of the player and appears to leave him off-balanced. Theres not alot of difference between that and an arm. Obviously dependant on the force used through the knee on the jump, but also whether there is an indaication of pushing. It's a close call. For me, this one looks like a foul. Obviously they are only stills so it is hard to judge.
the images show a definite foul. Probably a yellow card.
Dangerous play is an IFK offence and does not involve any contact. As soon as there is contact it changes from an IFK to a DFK offence. My take on still 3 is that the player puts his knee in the players back / shoulder. That makes it a DFK and probably a caution. That challenge could easily be considered reckless because of the height involved. A knee in the back of the head is really going to hurt!
As we all know, the fact that he wins the ball is no defence against the award of a free kick.
Of course we can only give what we see in real life. But if we're looking at a series of stills, then by definition we need to presume what has happened in between the stills to come to an informed opinion. In this case, it looks to me like the balance of probability is that the high knee made contact with the back of the player --> DFK and YC (or even theoretically RC). But can't be certain without a videoYes we know, as you've pointed out. But for me, the stills don't clearly show any contact. I make a judgement call based on what I see, not on a presumption.
True, but it's a good thing we're not making an actual decision and drawing an interpretation from imagesYes we know, as you've pointed out. But for me, the stills don't clearly show any contact. I make a judgement call based on what I see, not on a presumption.