3) Note that the HTC phone has the logo printed on the front. The iPhone does not. It's never had it on the front but even with the display off you know it's an iPhone. That means the front look is iconic even after the change from a 3.5" 4:3 display to a 4" 16:9 display. I think that's important.
True, the iPhone puts its big Apple logo on the back, where other people can see it. Most phones do that. It's like those car dealer logos they put on the back of automobiles to get free advertising (which I always make them remove).
As for the front, what makes it most recognizable as an iPhone (or iPad), is that single round Home button with the blank white app icon. The bezel can change, the colors can change,the size, the curves and borders... but that button is always there. It could have a round screen and the Home button would still give it away.
Now you make me think about other phones. For example, Samsung's motif that they've often used for many years, is to have a rather large primary button with chrome trim, surrounded by other buttons. The primary one used to be Select, now it's Home.