No, because your math is gibberish.
Yes. And you don't even need math to see it. You are missing the point.
Top half of image: In the rest frame of the light clock (i.e. anything at rest with it: in the same train - in your unattributed image) the pulse of light is bouncing between A and B, travelling L back and forth. This is not about seeing the pulse of light, it's just doing what the pulse is doing.
Bottom half of image: Considered from a different inertial frame, one where the train and the light clock are moving from left to right, the pulse of light makes a different path, travelling D back and forth.
D is longer than L.
But the speed of light was earlier shown to be invariant. For the same pulses of light to travel from A to B at the same speed, over different distances: it must be that time is relative.