... where Kennedy's hands are shown to be already rising as he reappears from behind the sign. His left hand is shown to be rising from about stomach level in earlier frames.
[Referring to the animation in 'Reply #24'] It is impossible to know whether Kennedy's right hand is rising or falling as it emerges from behind the Stemmons sign. As he goes behind the sign he is in the process of lowering his hand after waving so the probability is that his right hand is actually on the way down. There are many times where Kennedy's right hand is in exactly this position during the motorcade as demonstrated by the still photo in Reply #24. The bottom line is that you don't have the slightest clue what's happening with Kennedy's right hand as he emerges from behind the sign.
As for his left hand rising in earlier frames - that is 100% not true. It is not shown in Zapruder at all. Around z175 Kennedy's right arm is leaning over the side of the limo, his right hand clasping his left. He begins to wave with his right hand and his left stays resting on his stomach area until z225. Kennedy's hand begins to reflexively snap shut in this same frame and is fully closed in z226. Importantly, it is this frame where we see Kennedy's left elbow come up as he reacts to being shot.
He's Superman and catches the supersonic bullet in his right hand, then appears to be putting it in his mouth 